· EEM332

EEM332 Mikroişlemciler: 8086 Mimarisi, Yazmaçlar ve Sayı Sistemleri

EEM332 – Mikroişlemciler · 24.02.2003 · 18.10.2026

Bu yazı, Başkent Üniversitesi EEM332 Mikroişlemciler ders arşivindeki ilgili notları ve uygulamaları bir araya getiriyor (2003–2015). 8086/8088 tarihi, yazmaçlar, segmentler, bayraklar ve ikili-onaltılı sayı gösterimi. Belgelerin PDF arşiv kopyaları ve varsa kaynak kodları yazının sonunda ZIP olarak indirilebilir.

CPU02_2013

EEM332 Lecture2. History of Microprocessor Introduction to Intel 8086/8088 Registers of 8086 Simple instructions

8086 Microprocessor History

1959: first IC's 1971: µP 4004 4Bit Intel (~2000 Tr.) 1972: µP 8008 8Bit Intel (~5000 Tr.) 1974: µP 8080 8Bit Intel (~6000 Tr.) 1974: µP 6800 8Bit Motorola 1975: µP Z80 8Bit Zilog 1976: µP 9900 16Bit Texas Instruments 1978: µP 8086 16Bit Intel (50.000 Tr) 1982: µP 8286 16Bit Intel (100.000 Tr.) 1985: µP 80386 16Bit Intel (300.000 Tr.) 1989: µP 80486 16Bit Intel (10 Tr.) 1993: µP 80586 16Bit Intel (5·106 Tr.) ...

BRIEF HISTORY OF THE x86 FAMILY evolution from 8080/8085 to 8086

In 1978, Intel Corporation introduced the 16-bit 8086 microprocessor, a major

improvement over the previous generation 8080/8085 series. The 8086 capacity of 1 megabyte of memory exceeded the 8080/8085 maximum of 64K bytes of memory. 8080/8085 was an 8-bit system, which could work on only 8 bits of data at a time. Data larger than 8 bits had to be broken into 8-bit pieces to be processed by the

CPU.

8086 was a pipelined processor, as opposed to the nonpipelined 8080/8085

BRIEF HISTORY OF THE x86 FAMILY evolution from 8080/8085 to 8086

The microprocessor is typically a single VLSI (Very Large-Scale Integration) chip

MAXIMUM MINIMUM

MODE MODE

GND 1 40 Vcc GND 1 40 Vcc

AD14 AD15

A14 A15

AD13 A16,S3

A13 A16,S3

AD12 A17,S4

AD11 A18,S5 Dta Bus A11 A12 A17,S4

A18,S5

AD10 A19,S6

AD9 /BHE,S7

16 bit 8 bit A10 A19,S6 A9 high /SS0

AD8 MN,/MX

A8 MN,/MX

AD7 /RD

AD6 /RQ,/GT0 HOLD

8086 AD6 /RQ,/GT0 HOLD

AD5 /RQ,/GT1 HLDA

AD5

8088 /RQ,/GT1 HLDA

AD4 /LOCK /WR

AD3 /S2 IO/M

AD2 /S1 DT/R

AD1 /S0 /DEN

AD0 QS0 ALE

NMI QS1 /INTA

INTR /TEST

CLK                     READY
CLK                      READY

GND 20 21 RESET

Internal structure is same

Bus Interface Unit

Execution Unit (EU).

The BIU accesses memory and peripherals, while the EU executes instructions previously fetched.

The 8086 has two parts, the Bus Interface Unit (BIU) and the Execution Unit (EU).

The BIU fetches instructions, reads and writes data, and computes the 20-bit address.

The EU decodes and executes the instructions using the 16-bit

ALU.

The BIU contains the following registers:

IP - the Instruction Pointer CS – the Code Segment Register DS - the Data Segment Register SS - the Stack Segment Register ES - the Extra Segment Register

Software Model of the 8088/8086 Microprocessor

The status register, SR, with nine of its bits implement for status and control flags. The memory address space is 1 Mbytes and the I/O

address space is 64 Kbytes in length.

BIU registers 8086 Programmer’s Model (20 bit adder) ES Extra Segment CS Code Segment SS Stack Segment DS Data Segment IP Instruction Pointer

AX AH AL Accumulator BX BH BL Base Register CX CH CL Count Register DX DH DL Data Register SP Stack Pointer BP Base Pointer SI Source Index Register DI Destination Index Register

FLAGS

The first letter of each register indicates its use.

AX is used for the accumulator.

BX is a base addressing register.

CX is a counter in loop operations.

DX points to data in I/O operations

8086/88 internal registers 16 bits (2 bytes each)

AX, BX, CX and DX are two bytes wide and each byte can be accessed separately

These registers are used as memory pointers.

Flags will be discussed later

Segment registers are used as base address for a segment

in the 1 M byte of memory

Data Registers

The 8086/8088 Microprocessors: Registers

Registers

Registers are in the CPU and are referred to by specific names

Data registers

Hold data for an operation to be performed

There are 4 data registers (AX, BX, CX, DX)

Low and High bytes of the data registers (AX, BX, CX, DX) can be accessed

separately

AH, BH, CH, DH are the high bytes

AL, BL, CL, and DL are the low bytes

Address registers

Hold the address of an instruction or data element

Segment registers (CS, DS, ES, SS)

Pointer registers (SP, BP, IP)

Index registers (SI, DI)

Status register

Keeps the current status of the processor

On an IBM PC the status register is called the FLAGS register

In total there are fourteen 16-bit registers in an 8086/8088

Pointer and Index Registers

Contain the offset addresses of memory locations

Can also be used in arithmetic and other operations

SP: Stack pointer

Used with SS to access the stack segment

BP: Base Pointer

Primarily used to access data on the stack

Can be used to access data in other segments

SI: Source Index register

is required for some string operations

When string operations are performed, the SI register points to

memory locations in the data segment which is addressed by the DS register. Thus, SI is associated with the DS in string operations.

Segment Registers - CS, DS, SS and ES

Are Address registers

Store the memory addresses of instructions and data

Memory Organization

Each byte in memory has a 20 bit address starting with 0 to 220-1 or 1

meg of addressable memory

Addresses are expressed as 5 hex digits from 00000 - FFFFF

Problem: But 20 bit addresses are TOO BIG to fit in 16 bit registers!

Solution: Memory Segment

Block of 64K (65,536) consecutive memory bytes

A segment number is a 16 bit number

Segment numbers range from 0000 to FFFF

Within a segment, a particular memory location is specified with an offset

An offset also ranges from 0000 to FFFF

Generating a Memory Address

The BIU has a dedicated

adder for determining

physical memory addresses

Segments

Address

Segment Starting address is segment 0H register value shifted 4 places to the left.

CODE

64K Data

STACK                                Segment

DATA

EXTRA  CS:0

64K Code Segment Segment Registers

Segments are < or = 64K, can overlap, start at an address that ends in 0H. 0FFFFFH

MEMORY

The Code Segment

0H

4000H

CS: 0400H

IP 0056H 4056H

CS:IP = 400:56

Logical Address

Memory 0400 0 Segment Register

Offset + 0056 Physical or 04056H

0FFFFFH

Absolute Address

The offset is the distance in bytes from the start of the segment. The offset is given by the IP for the Code Segment. Instructions are always fetched with using the CS register.

The physical address is also called the absolute address.

The Data Segment

0H

05C00H

DS: 05C0

05C50H

EA 0050 DS:EA

Memory

05C0 0

Segment Register

Offset + 0050

Physical Address 0FFFFFH

05C50H

Data is usually fetched with respect to the DS register. The effective address (EA) is the offset. The EA depends on the addressing mode.

The Stack Segment

0H

0A00 0A000H

SS

0A100H

SP 0100 SS:SP

Memory

0A00 0

Segment Register

Offset + 0100

0FFFFFH

Physical Address 0A100H The offset is given by the SP register. The stack is always referenced with respect to the stack segment register. The stack grows toward decreasing memory locations. The SP points to the last or top item on the stack.

Logical Address is specified as segment:offset

Physical address is obtained by shifting the segment address 4 bits to the left and adding the

offset address

Thus the physical address of the logical address A4FB:4872 is A4FB0+ 4872 = A9822

INTRODUCTION TO PROGRAM SEGMENTS

A typical Assembly language program consists of

at least three segments

A code segment - which contains the Assembly language instructions that perform the tasks that the program was designed to accomplish. A data segment - used to store information (data) to be processed by the instructions in the code segment. A stack segment - used by the CPU to store information temporarily. The stack is a section of RAM,

A segment is an area of memory that includes up to 64K bytes, and begins on an
address evenly divisible by 16 (such an address ends in 0H)

8085 addressed a maximum of 64K of physical memory, since it had only 16 pins for address lines. (216 = 64K) Limitation was carried into 8088/86 design for compatibility.

In 8085 there was 64K bytes of memory for all code, data, and stack information.
In 8088/86 there can be up to 64K bytes in each category.

The code segment, data segment, and stack segment.

The Stack

The stack is implemented for temporary storage of information such as

data or addresses.

The stack is 64KBytes long and is organized from a software point of

view as 32K words.

The contents of the SP and BP registers are used as offsets into the stack

segment memory while the

segment base value is in the SS register. Push instructions (PUSH) and

pop instructions (POP)

Top of the stack (TOS) and bottom of the stack (BOS)

The 8088 can push word-wide data and address information onto the

stack from registers or memory.

Many stacks can exist but only one is active at a time.

As data is pushed onto the stack it is decremented.

As data is popped off the stack into the CPU, it is incremented.

Examples of ass. Language fo 8086

INTRODUCTION TO ASSEMBLY PROGRAMMING

Example for MOV instruction

This program first loads CL with value 55H, then moves this value around to various registers inside the CPU.

The use of 16-bit registers is shown here

Values cannot be loaded directly into any segment register (CS, DS, ES, or SS). To load a value into a segment register, load it to a non-segment register, then move it to the segment register

Flag register Many Assembly language instructions alter flag register bits & some instructions function differently based on the information in the flag register. The flag register is a 16-bit register sometimes referred to as the status register. Although 16 bits wide, only some of the bits are used. The rest are either undefined or reserved by Intel.

Carry flag Overflow Direction Parity flag

Interrupt enable Auxiliary flag 6 are status flags 3 are control flag Trap Zero

Sign Status flags (called conditional flags ): They are set according to some results of arithmetic operation. You do not need to alter the value yourself. Control flags: Used to control some operations of the MPU. These flags are to be set by you in order to achieve some specific purposes.

CF, the Carry Flag: This flag is set whenever there is a carry out, either from d7 after an 8-bit operation, or from d15 after a 16-bit data operation. PF, the Parity Flag: After certain operations, the parity of the result’s low-order byte is checked. If the byte has an even number of 1s, the parity flag is set to 1; otherwise, it is

cleared.

AF, the Auxiliary Carry Flag: If there is a carry from d3 to d4 of an operation this bit is set to 1, otherwise cleared (set to 0). ZF, the Zero Flag: The ZF is set to 1 if the result of the arithmetic or logical operation is zero, otherwise, it is cleared (set to 0). SF, the Sign Flag: MSB is used as the sign bit of the binary representation of the signed numbers.After arithmetic or logical operations the MSB is copied into SF to indicate the sign of the result. TF, the Trap Flag: When this flag is set it allows the program to single step, meaning to execute one instruction at a time. Used for debugging purposes. IF, Interrupt Enable Flag: This bit is set or cleared to enable or disable only the external interrupt requests. DF, the Direction Flag: This bit is used to control the direction of the string operations. OF, the Overflow Flag: This flag is set whenever the result of a signed number operation is too large, causing the high-order bit to overflow into the sign bit.

Not: the zero is used flag to implement program loops.

The status register, also called the flags register, indicate conditions that are produced as the result of executing an instruction. Only nine bits of the register are implemented. Six of these bits represent status flags and the other three bits represent control flags The 8088 provides instructions within its instruction set that are able to use these flags to alter the sequence in which the program is executed.

As an example, to add 5 bytes of data, a counter can be used to keep track of

how many times the loop needs to be repeated.

Each time the addition is performed the counter is decremented and the zero flag is checked. When the counter becomes zero, the zero flag is set (ZF = 1) and the loop is stopped.

CPU02_2013: sayfa 5, devre, tablo ve şekiller — CPU02_2013, sayfa 5.

CPU02_2013: sayfa 9, devre, tablo ve şekiller — CPU02_2013, sayfa 9.

cpu02_08

8086 Microprocessor History

History of Intel’s Microprocessors

Intel 4004

1971, 4-bit

Intel 8008

1972, 8-bit

Originally designed for Datapoint Corp. as a CRT display controller

Intel 8080

1974, April - Altair 8800, 1975, MITS( 256 bytes of Mem, $395)

Apple II -- Steve Jobs and Steve Wozniak 1976, Apple 사 설립

Bill Gates and a fellow student : BASIC, 1975 --> Microsoft

Intel 8086/8088

1978, 16 bit: 8088, 1979, 8-bit external bus

IBM PC ; 1981

29,000 Trs

Intel 80286

1982, 16-bit architecture

24-bit addressing, memory protection and virtual memory

16 MB of physical MEM and 1 GB of virtual mem

130,000 Trs onto a single chip

IBM PC/AT in 1984, IBM PS/2 Model 50 and 60

Intel 80386

1985, 32 bits

3~5 MIPS (7 MIPS on the 25 MHz chip)

memory paging and enhanced I/O permission features

4GB programming model

Intel 80486

1989 Spring COMDEX show -> 1990 June : actual release

1,200,000 Trs

386+387+8K data and instruction cache, paging and MMU

Pentium

1993

110 MIPS on 66 Mhz Chip

16 KB on-chip cache and 64 bit data bus

superscalar technology (two instructions/clock)

3.1 million transistors

Pentium Pro

1995, Superscalar(three-way issue)

5.5 million Trs in the CPU core + 15.5 million Trs in the secondary cache

8K data, 8K instr cache

256 KB SRAM secondary cache

200 SPECint92 at 133 MHz

2.9 V, 0.6 micron BICMOS

Pentium II

Pentium Pro + MMX, 1997

233, 266, upto 450 MHz

7.5 million Trs in CPU

512KB in secondary cache

Pentium III

1999

Pentium Pro + MMX + Internet Streaming SIMD Instructions

0.25 micron, 9.5 million Trs

600 MHz, 550 MHz,...

32 K(16K/16K) non-blocking level 1 cache

MAXIMUM MINIMUM

MODE MODE

GND 1 40 Vcc GND 1 40 Vcc

A14 A15

AD14 AD15

A13 A16,S3

AD13 A16,S3

A12 A17,S4

AD12 A17,S4

A11 A18,S5

AD11 A18,S5

A10 A19,S6

AD10 A19,S6

A9 high /SS0

AD9 /BHE,S7

A8 MN,/MX

AD8 MN,/MX

AD7 /RD

AD6 /RQ,/GT0 HOLD

AD6

8086

/RQ,/GT0 HOLD

AD5

8088 /RQ,/GT1 HLDA

AD5 /RQ,/GT1 HLDA

AD4 /LOCK /WR

AD3 /S2 IO/M

AD2 /S1 DT/R

AD1 /S0 /DEN

AD0 QS0 ALE

NMI QS1 /INTA

INTR /TEST

CLK                     READY
CLK                     READY

GND 20 21 RESET

Software Model of the 8088/8086 Microprocessor

The status register, SR, with nine of its bits implement for status and control flags. The memory address space is 1 Mbytes and the I/O

address space is 64 Kbytes in length.

The 8086 has two parts, the Bus Interface Unit (BIU) and the

Execution Unit (EU).

The BIU fetches instructions, reads and writes data, and computes the

20-bit address.

The EU decodes and executes the instructions using the 16-bit ALU.

The BIU contains the following registers:

IP - the Instruction Pointer CS – the Code Segment Register DS - the Data Segment Register SS - the Stack Segment Register ES - the Extra Segment Register

Bus Interface Unit

Execution Unit (EU).

8086 Programmer’s Model

ES Extra Segment BIU registers (20 bit adder) CS Code Segment SS Stack Segment DS Data Segment IP Instruction Pointer

AX AH AL Accumulator BX BH BL Base Register CX CH CL Count Register DX DH DL Data Register SP Stack Pointer BP Base Pointer SI Source Index Register DI Destination Index Register

FLAGS

8086/88 internal registers 16 bits (2 bytes each)

AX, BX, CX and DX are two bytes wide and each byte can be accessed separately

These registers are used as memory pointers.

Flags will be discussed later

Segment registers are used as base address for a segment

in the 1 M byte of memory

Data Registers

The 8086/8088 Microprocessors: Registers

Registers

Registers are in the CPU and are referred to by specific names

Data registers

Hold data for an operation to be performed

There are 4 data registers (AX, BX, CX, DX)

Address registers

Hold the address of an instruction or data element

Segment registers (CS, DS, ES, SS)

Pointer registers (SP, BP, IP)

Index registers (SI, DI)

Status register

Keeps the current status of the processor

On an IBM PC the status register is called the FLAGS register

In total there are fourteen 16-bit registers in an 8086/8088

Data Registers: AX, BX, CX, DX

Instructions execute faster if the data is in a register

AX, BX, CX, DX are the data registers

Low and High bytes of the data registers can be accessed

separately

AH, BH, CH, DH are the high bytes

AL, BL, CL, and DL are the low bytes

Data Registers are general purpose registers but they also

perform special functions

Accumulator Register

Preferred register to use in arithmetic, logic and data transfer instructions

because it generates the shortest Machine Language Code

Must be used in multiplication and division operations

Must also be used in I/O operations

BX .Base Register

Also serves as an address register

Used in array operations

Used in Table Lookup operations (XLAT)

CX : Count register

Used as a loop counter

Used in shift and rotate operations

DX : Data register

Used in multiplication and division

Also used in I/O operations

DI: Destination Index register is also required for some string operations. When string operations are performed, the DI register points to memory locations in the

data segment which is addressed by the ES register. Thus, DI is

associated with the ES in string operations. The SI and the DI registers may also be used to access data stored in arrays

Pointer and Index Registers

Contain the offset addresses of memory locations

Can also be used in arithmetic and other operations

SP: Stack pointer

Used with SS to access the stack segment

BP: Base Pointer

Primarily used to access data on the stack

Can be used to access data in other segments

SI: Source Index register

is required for some string operations

When string operations are performed, the SI register points to

memory locations in the data segment which is addressed by the DS register. Thus, SI is associated with the DS in string operations.

Segment Registers - CS, DS, SS and ES

Are Address registers

Store the memory addresses of instructions and data

Memory Organization

Each byte in memory has a 20 bit address starting with 0 to 220-1 or 1

meg of addressable memory

Addresses are expressed as 5 hex digits from 00000 - FFFFF

Problem: But 20 bit addresses are TOO BIG to fit in 16 bit registers!

Solution: Memory Segment

Block of 64K (65,536) consecutive memory bytes

A segment number is a 16 bit number

Segment numbers range from 0000 to FFFF

Within a segment, a particular memory location is specified with an offset

An offset also ranges from 0000 to FFFF

Generating a Memory

Address

The BIU has a dedicated

adder for determining

physical memory addresses

Segments

Address

Segment Starting address is segment 0H register value shifted 4 places to the left.

CODE

64K Data

STACK                                Segment

DATA

EXTRA  CS:0

64K Code Segment Segment Registers

Segments are < or = 64K, can overlap, start at an address that ends in 0H. 0FFFFFH

MEMORY

The Code Segment

0H

4000H

CS: 0400H

IP 0056H 4056H

CS:IP = 400:56

Logical Address

Memory 0400 0 Segment Register

Offset + 0056

Physical or 04056H

0FFFFFH

Absolute Address

The offset is the distance in bytes from the start of the segment. The offset is given by the IP for the Code Segment. Instructions are always fetched with using the CS register.

The physical address is also called the absolute address.

The Data Segment

0H

05C00H

DS: 05C0

05C50H

EA 0050 DS:EA

Memory

05C0 0

Segment Register

Offset + 0050

Physical Address 0FFFFFH

05C50H

Data is usually fetched with respect to the DS register. The effective address (EA) is the offset. The EA depends on the addressing mode.

The Stack Segment

0H

0A00 0A000H

SS

0A100H

SP 0100 SS:SP

Memory

0A00 0

Segment Register

Offset + 0100

0FFFFFH

Logical Address is specified as segment:offset

Physical address is obtained by shifting the segment address 4 bits to the left and adding the

offset address

Thus the physical address of the logical address A4FB:4872 is A4FB0+ 4872 = A9822

The Stack

The stack is implemented for temporary storage of information such as

data or addresses.

The stack is 64KBytes long and is organized from a software point of

view as 32K words.

The contents of the SP and BP registers are used as offsets into the stack

segment memory while the

segment base value is in the SS register. Push instructions (PUSH) and

pop instructions (POP)

Top of the stack (TOS) and bottom of the stack (BOS)

The 8088 can push word-wide data and address information onto the

stack from registers or memory.

Many stacks can exist but only one is active at a time.

Assembly

Flags in flag register

Carry flag Overflow Direction Parity flag

Interrupt enable Auxiliary flag 6 are status flags 3 are control flag Trap Zero

Sign

Status flags

They are set according to some results of arithmetic operation. You do not need to alter the value yourself.

Control flags

Used to control some operations of the MPU. These flags are to be set by you in order to achieve some specific purposes.

cleared.

Data Types

The most significant bit of a signed integer is a sign bit. A zero in this bit position identifies a positive number.

The 8088 can also process data that is coded as binary-coded decimal (BCD) numbers.

cpu03-06

8086 Microprocessor History

History of Intel’s Microprocessors

Intel 4004

1971, 4-bit

Intel 8008

1972, 8-bit

Originally designed for Datapoint Corp. as a CRT display controller

Intel 8080

1974, April - Altair 8800, 1975, MITS( 256 bytes of Mem, $395)

Apple II -- Steve Jobs and Steve Wozniak 1976, Apple 사 설립

Bill Gates and a fellow student : BASIC, 1975 --> Microsoft

Intel 8086/8088

1978, 16 bit: 8088, 1979, 8-bit external bus

IBM PC ; 1981

29,000 Trs

Intel 80286

1982, 16-bit architecture

24-bit addressing, memory protection and virtual memory

16 MB of physical MEM and 1 GB of virtual mem

130,000 Trs onto a single chip

IBM PC/AT in 1984, IBM PS/2 Model 50 and 60

Intel 80386

1985, 32 bits

3~5 MIPS (7 MIPS on the 25 MHz chip)

memory paging and enhanced I/O permission features

4GB programming model

Intel 80486

1989 Spring COMDEX show -> 1990 June : actual release

1,200,000 Trs

386+387+8K data and instruction cache, paging and MMU

Pentium

1993

110 MIPS on 66 Mhz Chip

16 KB on-chip cache and 64 bit data bus

superscalar technology (two instructions/clock)

3.1 million transistors

Pentium Pro

1995, Superscalar(three-way issue)

5.5 million Trs in the CPU core + 15.5 million Trs in the secondary cache

8K data, 8K instr cache

256 KB SRAM secondary cache

200 SPECint92 at 133 MHz

2.9 V, 0.6 micron BICMOS

Pentium II

Pentium Pro + MMX, 1997

233, 266, upto 450 MHz

7.5 million Trs in CPU

512KB in secondary cache

Pentium III

1999

Pentium Pro + MMX + Internet Streaming SIMD Instructions

0.25 micron, 9.5 million Trs

600 MHz, 550 MHz,...

32 K(16K/16K) non-blocking level 1 cache

8086 Microprocessor

16-bit Arithmetic Logic Unit

16-bit data bus

(8088 has 8-bit data bus)

20-bit address bus -

220 = 1,048,576 = 1 meg

8086 Architecture

The 8086 has two parts, the Bus Interface Unit (BIU) and the

Execution Unit (EU).

The BIU fetches instructions, reads and writes data, and computes the

20-bit address.

The EU decodes and executes the instructions using the 16-bit ALU.

The BIU contains the following registers:

IP - the Instruction Pointer CS - the Code Segment Register DS - the Data Segment Register SS - the Stack Segment Register ES - the Extra Segment Register

The BIU fetches instructions using the CS and IP, written CS:IP, to contruct the 20-bit address. Data is fetched using a segment register (usually the DS)

and an effective address (EA) computed by the EU depending on the
addressing mode.

80386/80486/Pentium Registers

The ax, bx, cx, dx, si, di, bp, sp, flags, and ip 32 bits registers of the 8068 were all extended to 32 bits. The 80386 calls these new 32 bit versions EAX,

EBX, ECX, EDX, ESI, EDI, EBP, ESP,

EFLAGS, and EIP Memory segments can be as large as 4GB

8086 Programmer’s Model

ES Extra Segment BIU registers CS Code Segment (20 bit adder) SS Stack Segment DS Data Segment IP Instruction Pointer

AX AH AL Accumulator BX BH BL Base Register CX CH CL Count Register DX DH DL Data Register SP Stack Pointer BP Base Pointer SI Source Index Register DI Destination Index Register

FLAGS

8086/88 8086/88internal internalregisters registers16 16bits bits(2 (2bytes byteseach) each)

AX, BX, CX and DX are two bytes wide and each byte can be accessed separately

These registers are used as memory pointers.

Flags will be discussed later

Segment registers are used as base address for a segment

in the 1 M byte of memory

The 8086/8088 Microprocessors: Registers

Registers

Registers are in the CPU and are referred to by specific names

Data registers

Hold data for an operation to be performed

There are 4 data registers (AX, BX, CX, DX)

Address registers

Hold the address of an instruction or data element

Segment registers (CS, DS, ES, SS)

Pointer registers (SP, BP, IP)

Index registers (SI, DI)

Status register

Keeps the current status of the processor

On an IBM PC the status register is called the FLAGS register

In total there are fourteen 16-bit registers in an 8086/8088

Data Registers: AX, BX, CX, DX

Instructions execute faster if the data is in a register

AX, BX, CX, DX are the data registers

Low and High bytes of the data registers can be accessed

separately

AH, BH, CH, DH are the high bytes

AL, BL, CL, and DL are the low bytes

Data Registers are general purpose registers but they also

perform special functions

Accumulator Register

Preferred register to use in arithmetic, logic and data transfer instructions

because it generates the shortest Machine Language Code

Must be used in multiplication and division operations

Must also be used in I/O operations

Base Register

Also serves as an address register

Used in array operations

Used in Table Lookup operations (XLAT)

Count register

Used as a loop counter

Used in shift and rotate operations

Data register

Used in multiplication and division

Also used in I/O operations

Pointer and Index Registers

Contain the offset addresses of memory locations

Can also be used in arithmetic and other operations

SP: Stack pointer

Used with SS to access the stack segment

BP: Base Pointer

Primarily used to access data on the stack

Can be used to access data in other segments

SI: Source Index register

is required for some string operations

When string operations are performed, the SI register points to

memory locations in the data segment which is addressed by the DS register. Thus, SI is associated with the DS in string operations.

DI: Destination Index register

is also required for some string operations.

When string operations are performed, the DI register points to

memory locations in the data segment which is addressed by the ES register. Thus, DI is associated with the ES in string operations.

The SI and the DI registers may also be used to access data

stored in arrays

Segment Registers - CS, DS, SS and ES

Are Address registers

Store the memory addresses of instructions and data

Memory Organization

Each byte in memory has a 20 bit address starting with 0 to 2 20-1 or 1

meg of addressable memory

Addresses are expressed as 5 hex digits from 00000 - FFFFF

Problem: But 20 bit addresses are TOO BIG to fit in 16 bit registers!

Solution: Memory Segment

Block of 64K (65,536) consecutive memory bytes

A segment number is a 16 bit number

Segment numbers range from 0000 to FFFF

Within a segment, a particular memory location is specified with an offset

An offset also ranges from 0000 to FFFF

Intel Memory Address Generation

The BIU has a dedicated adder for determining physical

memory addresses

If the data segment starts at location 1000h and a data reference

contains the address 29h where is the actual data?

Offset Value (16 bits)

Segment Register (16 bits) 0000

2 9

Adder

Offset: 0000000000101001

Segment 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 00 0 0 0 : Physical Address (20 Bits)

Address: 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 01 0 0 1

Segments

Address
0H

Segment Starting address is segment

CODE

64K Data

STACK                                  Segment

DATA

EXTRA  CS:0

64K Code Segment Segment Registers

Segments are < or = 64K, can overlap, start at an address that ends in 0H. 0FFFFFH

MEMORY

The Code Segment

0H

4000H

CS: 0400H

IP 0056H 4056H

CS:IP = 400:56

Logical Address

Memory 0400 0 Segment Register

Offset + 0056 Physical or 04056H 0FFFFFH Absolute Address

The offset is the distance in bytes from the start of the segment. The offset is given by the IP for the Code Segment. Instructions are always fetched with using the CS register.

The physical address is also called the absolute address.

The Data Segment

0H

05C00H

DS: 05C0

05C50H

EA 0050 DS:EA

Memory

05C0 0

Segment Register

Offset + 0050

Physical Address 05C50H 0FFFFFH

Data is usually fetched with respect to the DS register. The effective address (EA) is the offset. The EA depends on the addressing mode.

The Stack Segment

0A00 0A000H 0H

SS

0A100H

SP 0100 SS:SP

Memory

0A00 0

Segment Register

Offset + 0100

Physical Address 0A100H 0FFFFFH

The offset is given by the SP register. The stack is always referenced with respect to the stack segment register. The stack grows toward decreasing memory locations. The SP points to the last or top item on the stack.

Logical Address is specified as segment:offset

Physical address is obtained by shifting the segment address 4 bits to the left and adding the

offset address

Thus the physical address of the logical address A4FB:4872 is A4FB0+ 4872 = A9822

LOGICAL ADDRESS PHYSICAL ADDRESS

Segment Beginning Last Beginning Last Number Address Address Address Address

0000 0000:0000 0000:FFFF 00000 0FFFF

0001 0001:0000 0001:FFFF 00010 1000F

0002 0002:0000 0002:FFFF 00020 1001F

0003 0003:0000 0003:FFFF 00030 1002F

. . . . . . . . . . . . . . .

FFFF FFFF:0000 FFFF:FFFF FFFF0 0FFEF

Flags Flags in

in flag

flag register register

Carry flag Overflow Direction Parity flag Interrupt enable Auxiliary flag Trap Zero

6 are status flags Sign 3 are control flag

Flag Register

Conditional flags:

They are set according to some results of arithmetic operation. You do

not need to alter the value yourself.

Control flags:

Used to control some operations of the MPU. These flags are to be set

by you in order to achieve some specific purposes. Flag O D I T S Z A P C

Bit no. 15 14 13 12 11 9 8 7 6 5 4 3 2 1 0

CF (carry) Contains carry from leftmost bit following

arithmetic, also contains last bit from a shift or rotate operation.

Flag Register

OF (overflow) Indicates overflow of the

leftmost bit during arithmetic.

DF (direction) Indicates left or right for

moving or comparing string data.

IF (interrupt) Indicates whether external

interrupts are being processed or ignored.

TF (trap) Permits operation of the processor

in single step mode.

SF (sign) Contains the resulting sign of an

arithmetic operation (1=negative)

ZF (zero) Indicates when the result of

arithmetic or a comparison is zero. (1=yes)

AF (auxiliary carry) Contains carry out of

bit 3 into bit 4 for specialized arithmetic.

PF (parity) Indicates the number of 1 bits

that result from an operation.

cpu02

Representation of Numbers and
Characters

Number Systems

A. Decimal

B. Binary

C. Hexadecimal

Is a short-hand notation for binary

Consists of 16 digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C,

D, E, F

Note: Yu's book use:

101d to represent decimal

101b to represent binary

101h to represent hexadecimal

Conversion between number systems

A. Binary to Decimal

B. Decimal to Binary

C. Hexadecimal to Decimal

D. Decimal to Hexadecimal

E. Binary to Hex

F. Hex to Binary

Note: we will learn addition and subtraction in

hexadecimal only

Terminology

MSB - most significant bit is bit 15 in a word or bit 7 in a

byte

LSB - least significant bit is bit 0 in both a word and a byte

(If the LSB of an integer is 0, the integer is even. If its LSB is a 1, the integer is odd)

Representing Integers

Unsigned Integers

Integers that are never negative

Memory addresses, counters, and ASCII character codes are stored

as unsigned numbers

No bit is needed to represent the sign bit

Largest unsigned integer in a byte is 11111111b or 255 or 28 -1;

in a word it is 1111111111111111b or 65,535 or 216 - 1

Signed Integers

In a signed number the MSB is the sign. The number is positive if

the MSB is a 0 and the number is negative if the MSB is a One's complement in binary

flip all the bits from 0 to 1 or from 1 to 0

Two's complement in binary -

get one's complement and then add 1 (that is, flip all the

bits and then add 1)

Representing Positive and Negative Numbers in Hex

Positive numbers - straight conversion to hex

Negative numbers are stored in two's complement form

To get the two's complement form of a number in hex:

First: Represent the number as if it were positive

Second: Subtract it from FF(byte) or FFFF(word)

Third: Add 1

Examples:

-97 as a word is FFFF -0061

FF9E

+ 1

FF9F = -97

-97 as a byte is FF -61

9E

9F = - 97

Advantage of Storing Numbers in 2’s Complement Form

Advantage of storing numbers in 2's complement form is

that subtraction can be accomplished by bit complementation and addition

Circuits for complementation and addition are easy to

design

Also the same addition circuit can be used for subtraction

as well. Hence, no separate circuit is needed for subtration

Interpreting Signed and Unsigned Bytes and Words in Memory as Decimal Numbers

Unsigned

Straight translation from binary or hex to decimal

Signed numbers

First determine the sign of the number by looking at its MSB. If

its 0, its positive and you can do a straight translation from binary

or hex to decimal

If its MSB is a 1, its negative and you must Re-complement it!

Since everything you see in memory will be expressed in

hexadecimal, you won't "see" the MSB. Instead, you will see a hex digit. Therefore, if the first hex digit of a signed word or a byte is 0 to 7, the number is positive. If the first hex digit of a signed word or a byte is 8 to F, the number is negative. Why?

Identifying Positive Integers in Hex First Hex Digit Expressed in Binary 0 0000 1 0001 2 0010 3 0011 4 0100 5 0101 6 0110 7 0111

In all of the above cases, the MSB is 0!

Therefore, if the first hex digit of a signed word or a byte is

0 to 7, the number is positive.

Identifying Negative Integers in Hex First Hex Digit Expressed in Binary 8 1000 9 1001

A 1010

B 1011

C 1100

D 1101

E 1110

F 1111

In all of the above cases, the MSB is 1 !

Therefore, if the first hex digit of a signed word or a byte is

8 to F, the number is positive

How to Interpret a Negative Integer Given in Hex

Re-complement the number in hex. To do that,

First: Subtract the byte or word from FF or FFFF respectively

Second: Add 1

Interpret your hex answer as a decimal answer and place a

minus sign in front of your answer!

Example: What signed number does the byte AAh

represent?
FF

-AA Subtract from all F's + 1 Add 1 56h Interpret your HEX answer as a decimal number So the answer is: -86

How to Interpret a Negative Integer Given in Binary

Re-complement the number in binary. To do that,

First: Flip all the bits

Second: Add 1

Interpret your binary answer as a decimal answer and place a

minus sign in front of your answer!

Example: What signed number does the byte 11111000b

represent?

Flip all bits 00000111b

Add 1          00001000b

So the answer is: -8

Range of Integers

The range of signed values that can be stored in a byte is

from -128 to 127

The range of signed values that can be stored in a word is

from -32,768 to 32,767

Character Representation

Code chosen for IBM PC is the ASCII code

7 bit code

27 or 128 possible values

stored in a byte

95 ASCII codes are printable (32 to 126)

0 to 31 and 127 are used for control purposes

IBM PC uses an extended character set using an 8 bit code

thus in can represent 28 or 256 possible values

ASCII keyboard

Each key pressed is stored in ASCII code

Today on IBM PC, each key is assigned a unique number called a

scan code to handle the many control and function keys in addition to the ASCII character keys

ASCII Codes for Capital Letters

Capital Letters of the Alphabet (41 - 5A)

A - 41 J - 4A Q - 51 Z - 5A

B - 42 K - 4B R - 52

C - 43 L - 4C S - 53

D - 44 M - 4D T - 54

E - 45 N - 4E U - 55

F - 46 0 - 4F V - 56

G - 47 P - 50 W - 57

H - 48 X - 58

I - 49 Y - 59

ASCII Codes for Lower Case Letters

Lower case letters of the alphabet (61-7A)

a - 61 j - 6A q - 71 z - 7A b - 62 k - 6B r - 72 c - 63 l - 6C s - 73 d - 64 m - 6D t - 74 e - 65 n - 6E u - 75 f - 66 o - 6F v - 76 g - 67 p - 70 w - 77 h - 68 x - 78 i - 69 y - 79

ASCII Codes for Digits and Special Characters

Digits (30-39)

0 - 30 3 - 33 6 - 36 9 - 39 1 - 31 4 - 34 7 - 37 2 - 32 5 - 35 8 - 38

Special Characters

space - 20 ! - 21

+ - 2B

- - 2D

See pages 442-443 in Yu's book for the complete ASCII

CODE chart

Practice Problems on ASCII Code

Interpret this: 31 32 33 20 4F 41 4B 20 53 54 52 45 45 54

Interpret this: 49 53 4E 27 54 20 54 48 49 53 20 46 55 4E 21

Homework - Number System Review

Conversion

1. Convert from decimal to binary

a. 43 b. 167

2. Convert from binary to decimal

a. 1101100b b. 1100011b

3. Convert from decimal to hexadecimal

a. 6242 b. 12321

4. Convert from hexadecimal to decimal

a. 4BFh b. A2F7h

5. Convert from binary to hexadecimal

a. 110010011110b b. 100001011b

6. Convert from hexadecimal to binary

a. FADh b. 265Ch c. BE98h

Homework: Data Representations Set 1 Problems Note: Express all answers to problems 1-9 in HEXADECIMAL

1. How do you represent 231 as an unsigned byte? ___________

2. How do you represent 110 as a signed byte? ___________

3. How do you represent -103 as a signed byte? ___________

4. How do you represent 64785 as an unsigned word? _______

5. How do you represent 1600 as a signed word? ___________

6. How do you represent -160 as a signed word? _________

7. How do you represent +7623 as a character string?_________

8. How do you represent -632 as a character string? _______

9. How do you represent WOW! as a character string? _______

Homework: Hex to Decimal or Character - Set 1 You are looking at a dump. Therefore, the values in problems 10-16 are expressed in HEXADECIMAL. Express your answers to problems 10-16 in

decimal or character form:

10. You know 8E is an unsigned byte. What number does it represent? ______

11. You know 8E is a signed byte. What number does it represent? _________

12. You know 7E is a signed byte. What number does it represent? _________

13. You know 34A2 is an unsigned word (PV). What number does

it represent? _________

14. You know 34A2 is a signed word (PV). What number does it

represent? _________

15. You know 3452 is a signed word (PV). What number does it

represent? _________

16. You know 5745 is a character string. What value does it

represent? _________

Homework: Hex to Decimal or Character - Set 1 (cont’d) You are looking at a dump. Therefore, the values in problems 10-16 are expressed in HEXADECIMAL. Express your anwers to problems 10-16 in

decimal or character form:
Answers

10. You know 8E is an unsigned byte. What number does it represent? 142

11. You know 8E is a signed byte. What number does it represent? -114

12. You know 7E is a signed byte. What number does it represent? 126

13. You know 34A2 is an unsigned word (PV). What number does

it represent? 41524

14. You know 34A2 is a signed word (PV). What number does it

represent?       -24012

15. You know 3452 is a signed word (PV). What number does it

represent?       21044

16. You know 5745 is a character string. What value does it

represent?       WE

HOMEWORK: Data Representations - Set 2 LV: Logical View PV: Physical View Express all answers to problems 1-9 in HEXADECIMAL

1. How do you represent 195 as an unsigned byte? ___________

2. How do you represent 101 as a signed byte? ___________

3. How do you represent -119 as a signed byte? ___________

4. How do you represent 42623 as an unsigned word? (LV)______

5. How do you represent 32001 as a signed word? (LV)__________

6. How do you represent -1675 as a signed word? (LV) _________

7. How do you represent +25 as a character string?_______

8. How do you represent -413 as a character string? _______

9. How do you represent (TEST) as a character string? ______

Hex to Decimal or Character: Set 2 You are looking at a dump. Therefore, the values in problems 10-16 are expressed in HEXADECIMAL. Express your answers to problems 10-16 in

decimal or character form:

10. You know 95 is an unsigned byte. What number does it represent? ____

11. You know 95 is a signed byte. What number does it represent? _____

12. You know 7F is a signed byte. What number does it represent? _____

13. You know 1DB1 is an unsigned word (PV). What number does

it represent? ______

14. You know 1DB1 is a signed word (PV). What number does it

represent? ______

15. You know 6C73 is a signed word (PV). What number does it

represent? ______

16. You know 4D41 is a character string. What value does it

represent? ______

cpu02-06

Representation of Numbers and
Characters

Number Systems

A. Decimal

B. Binary

C. Hexadecimal

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F

Note: • MSB - most significant bit

101d to represent decimal is bit 15 in a word or bit 7

101b to represent binary in a byte

101h to represent hexadecimal

Conversion between number systems

LSB - least significant bit

A. Binary to Decimal is bit 0 in both a word and

B. Decimal to Binary

a byte (If the LSB of an

C. Hexadecimal to Decimal

D. Decimal to Hexadecimal

integer is 0, the integer is

E. Binary to Hex even. If its LSB is a 1, the

F. Hex to Binary integer is odd)

Note: we will learn addition and subtraction in hexadecimal only

Representing Integers

Unsigned Integers

Integers that are never negative

Memory addresses, counters, and ASCII character codes are stored

as unsigned numbers

No bit is needed to represent the sign bit

Largest unsigned integer in a byte is 11111111b or 255 or 28 -1;

in a word it is 1111111111111111b or 65,535 or 216 - 1

Signed Integers

In a signed number the MSB is the sign. The number is positive if

the MSB is a 0 and the number is negative if the MSB is a One's complement in binary

flip all the bits from 0 to 1 or from 1 to 0

Two's complement in binary -

get one's complement and then add 1 (that is, flip all the

bits and then add 1)

Representing Positive and Negative Numbers in Hex

Positive numbers - straight conversion to hex

Negative numbers are stored in two's complement form

To get the two's complement form of a number in hex:

First: Represent the number as if it were positive

Second: Subtract it from FF(byte) or FFFF(word)

Third: Add 1

Examples:

-97 as a word is FFFF -0061

FF9E

+ 1

FF9F = -97

-97 as a byte is FF -61

9E

9F = - 97

Advantage of Storing Numbers in 2’s Complement Form

Advantage of storing numbers in 2's complement form is

that subtraction can be accomplished by bit complementation and addition

Circuits for complementation and addition are easy to

design

Also the same addition circuit can be used for subtraction

as well. Hence, no separate circuit is needed for subtration

Interpreting Signed and Unsigned Bytes and Words in Memory as Decimal Numbers

Unsigned

Straight translation from binary or hex to decimal

Signed numbers

First determine the sign of the number by looking at its MSB. If

its 0, its positive and you can do a straight translation from binary

or hex to decimal

If its MSB is a 1, its negative and you must Re-complement it!

Since everything you see in memory will be expressed in

Identifying Positive Integers in Hex First Hex Digit Expressed in Binary 0 0000 1 0001 2 0010 3 0011 4 0100 5 0101 6 0110 7 0111

In all of the above cases, the MSB is 0!

Therefore, if the first hex digit of a signed word or a byte is

0 to 7, the number is positive.

Identifying Negative Integers in Hex First Hex Digit Expressed in Binary 8 1000 9 1001

A 1010

B 1011

C 1100

D 1101

E 1110

F 1111

In all of the above cases, the MSB is 1 !

Therefore, if the first hex digit of a signed word or a byte is

8 to F, the number is positive

How to Interpret a Negative Integer Given in Hex

Re-complement the number in hex. To do that,

First: Subtract the byte or word from FF or FFFF respectively

Second: Add 1

Interpret your hex answer as a decimal answer and place a

minus sign in front of your answer!

Example: What signed number does the byte AAh

represent?
FF

-AA Subtract from all F's + 1 Add 1 56h Interpret your HEX answer as a decimal number So the answer is: -86

How to Interpret a Negative Integer Given in Binary

Re-complement the number in binary. To do that,

First: Flip all the bits

Second: Add 1

Interpret your binary answer as a decimal answer and place a

minus sign in front of your answer!

Example: What signed number does the byte 11111000b

represent?

Flip all bits 00000111b

Add 1          00001000b

So the answer is: -8

Range of Integers

The range of signed values that can be stored in a byte is

from -128 to 127

The range of signed values that can be stored in a word is

from -32,768 to 32,767

Character Representation

Code chosen for IBM PC is the ASCII code

7 bit code

27 or 128 possible values

stored in a byte

95 ASCII codes are printable (32 to 126)

0 to 31 and 127 are used for control purposes

IBM PC uses an extended character set using an 8 bit code

thus in can represent 28 or 256 possible values

ASCII keyboard

Each key pressed is stored in ASCII code

Today on IBM PC, each key is assigned a unique number called a

scan code to handle the many control and function keys in addition to the ASCII character keys

ASCII Codes for Capital Letters

Capital Letters of the Alphabet (41 - 5A)

A - 41 J - 4A Q - 51 Z - 5A

B - 42 K - 4B R - 52

C - 43 L - 4C S - 53

D - 44 M - 4D T - 54

E - 45 N - 4E U - 55

F - 46 0 - 4F V - 56

G - 47 P - 50 W - 57

H - 48 X - 58

I - 49 Y - 59

ASCII Codes for Lower Case Letters

Lower case letters of the alphabet (61-7A)

a - 61 j - 6A q - 71 z - 7A b - 62 k - 6B r - 72 c - 63 l - 6C s - 73 d - 64 m - 6D t - 74 e - 65 n - 6E u - 75 f - 66 o - 6F v - 76 g - 67 p - 70 w - 77 h - 68 x - 78 i - 69 y - 79

ASCII Codes for Digits and Special Characters

Digits (30-39)

0 - 30 3 - 33 6 - 36 9 - 39 1 - 31 4 - 34 7 - 37 2 - 32 5 - 35 8 - 38

Special Characters

space - 20 ! - 21

+ - 2B

- - 2D

See pages 442-443 in Yu's book for the complete ASCII

CODE chart

Homework - Number System Review

Conversion

1. Convert from decimal to binary

a. 43 b. 167

2. Convert from binary to decimal

a. 1101100b b. 1100011b

3. Convert from decimal to hexadecimal

a. 6242 b. 12321

4. Convert from hexadecimal to decimal

a. 4BFh b. A2F7h

5. Convert from binary to hexadecimal

a. 110010011110b b. 100001011b

6. Convert from hexadecimal to binary

a. FADh b. 265Ch c. BE98h

Homework: Data Representations Set 1 Problems Note: Express all answers to problems 1-9 in HEXADECIMAL

1. How do you represent 231 as an unsigned byte? ___________

2. How do you represent 110 as a signed byte? ___________

3. How do you represent -103 as a signed byte? ___________

4. How do you represent 64785 as an unsigned word? _______

5. How do you represent 1600 as a signed word? ___________

6. How do you represent -160 as a signed word? _________

7. How do you represent +7623 as a character string?_________

8. How do you represent -632 as a character string? _______

9. How do you represent WOW! as a character string? _______

Practice Problems on ASCII Code

Interpret this: 31 32 33 20 4F 41 4B 20 53 54 52 45 45 54

Interpret this: 49 53 4E 27 54 20 54 48 49 53 20 46 55 4E 21

Homework: Hex to Decimal or Character - Set 1 You are looking at a dump. Therefore, the values in problems 10-16 are expressed in HEXADECIMAL. Express your answers to problems 10-16 in

decimal or character form:

10. You know 8E is an unsigned byte. What number does it represent? ______

11. You know 8E is a signed byte. What number does it represent? _________

12. You know 7E is a signed byte. What number does it represent? _________

13. You know 34A2 is an unsigned word (PV). What number does

it represent? _________

14. You know 34A2 is a signed word (PV). What number does it

represent? _________

15. You know 3452 is a signed word (PV). What number does it

represent? _________

16. You know 5745 is a character string. What value does it

represent? _________

Homework: Hex to Decimal or Character - Set 1 (cont’d) You are looking at a dump. Therefore, the values in problems 10-16 are expressed in HEXADECIMAL. Express your anwers to problems 10-16 in

decimal or character form:
Answers

10. You know 8E is an unsigned byte. What number does it represent? 142

11. You know 8E is a signed byte. What number does it represent? -114

12. You know 7E is a signed byte. What number does it represent? 126

13. You know 34A2 is an unsigned word (PV). What number does

it represent? 41524

14. You know 34A2 is a signed word (PV). What number does it

represent?       -24012

15. You know 3452 is a signed word (PV). What number does it

represent?       21044

16. You know 5745 is a character string. What value does it

represent?       WE

HOMEWORK: Data Representations - Set 2 LV: Logical View PV: Physical View Express all answers to problems 1-9 in HEXADECIMAL

1. How do you represent 195 as an unsigned byte? ___________

2. How do you represent 101 as a signed byte? ___________

3. How do you represent -119 as a signed byte? ___________

4. How do you represent 42623 as an unsigned word? (LV)______

5. How do you represent 32001 as a signed word? (LV)__________

6. How do you represent -1675 as a signed word? (LV) _________

7. How do you represent +25 as a character string?_______

8. How do you represent -413 as a character string? _______

9. How do you represent (TEST) as a character string? ______

Hex to Decimal or Character: Set 2 You are looking at a dump. Therefore, the values in problems 10-16 are expressed in HEXADECIMAL. Express your answers to problems 10-16 in

decimal or character form:

10. You know 95 is an unsigned byte. What number does it represent? ____

11. You know 95 is a signed byte. What number does it represent? _____

12. You know 7F is a signed byte. What number does it represent? _____

13. You know 1DB1 is an unsigned word (PV). What number does

it represent? ______

14. You know 1DB1 is a signed word (PV). What number does it

represent? ______

15. You know 6C73 is a signed word (PV). What number does it

represent? ______

16. You know 4D41 is a character string. What value does it

represent? ______