Question

MATCH THE DESCRIPTION OF EACH TERM

1 ID   

2 STACK

3 SEGMENT REGISTER

4 GENERAL REGISTER

5 POP INSTRUCTION ACTS LIKE

6 PUSH INSTRUCTION ACTS LIKE

A READ

B ES

C TRANSLATE INSTRUCTIONS

D STORAGE AREA

E DX

F WRITE

Answer 1

DESCRIPTION OF EACH TERM:-

1:- ID:-id is a selector used to specify a particular data on any file. An id may be a word, number, letter, symbol, or any combination of those.

2:- STACK:-A stack is an Abstract Data type (ADT).Stacks work on the “Last in, First out”.Stack is a linear data structure which follows a order in which the operations are performed.

Some are the main operations :

• push(value) : add an element on the top of the stack.
• pop () : removes the top element of the stack.
• top() : returns the top value without removing it.
• empty() : returns true if stack has no elements.
• size() : returns the number of elements in stack.

3:- SEGMENT REGISTER:-In processors has the memory divided into various sections called as segments.All x86 segment registers are 16 bits in size.

• CS(code segment):- segment address of the code segment of the currently executing instruction is contained in Code Segment.Machine instructions exist at some offset into a code segment.

• DS(data segment):- There may be many data segments, but the CPU may only use one at a time, by placing the segment address of that segment in register Data Segment.Variables and other data exist at some offset into a data segment.

• SS( stack segment):- The stack is a very important component of the CPU used for temporary storage of data and addresses. Therefore, the stack has a segment address, which is contained in register SS.

• ES(extra segment):- a spare segment that may be used for specifying a location in memory.

4:-GENERAL REGISTER:-

General registers is used to store temporary data. While the instructions are executed in the control unit, they may work on some numeric value or some operands. These need to be stored somewhere so that the processor can operate on them easily. So, these registers are used in these cases. There are 4 general egisters of 16-bit length each. Each of them is further divided into two subparts of 8-bit length each one high, which stores the higher-order bits and another low which stores the lower order bits.

1. AX = [AH:AL]
2. BX = [BH:BL]
3. CX = [CH:CL]
4. DX = [DH:DL]

5:- POP INSTRUCTION:-Pop is taking out the value stored. Popping means restoring whatever is on top of the stack into a register.

eg:-

push eax
mov eax, ebx
pop ebx

6 PUSH INSTRUCTION:-Pushing means forcing a value to get stored to some location.Pushing a value means writing it to the stack.

eg:-

push eax
mov eax, ebx
pop ebx

A) READ:- Memory unit supports two basic operations:- read and write. Read operation reads previously stored data.Operation requires a memory address.

Read Cycle:

1. Place the address of the location to be read on the address bus,

2. Activate the memory read control signal on the control bus,

3. Wait for the memory to retrieve the data from the addressed memory location and place them on the data bus,

4. Read the data from the data bus,

5. Drop the memory read control signal to terminate the read cycle.

B) ES:- It stands for Extra Segment. ES is add-on data segment, which is used by the string to hold the extra data.

A spare segment that may be used for specifying a location in memory.

C) TRANSLATE INSTRUCTIONS:-XLAT  replaced a byte in the AL register with a byte from a user-coded translation table. When XLAT is executed, AL have the unsigned index to the table addressed by EBX. XLAT change the contents of AL from table index to table entry. EBX is unchanged. The XLAT instruction is useful for translating from one coding system to another such as from ASCII to EBCDIC. The translate table may be up to 256 bytes long. The value placed in the AL register serves as an index to the location of the corresponding translation value.

D) STORAGE AREA:-scratchpad refers to a special high-speed memory circuit used to hold small item of data for speedy retrieval.System area contains programs on either a read-only memory or flash memory. EEPROM, and areas of read/write (RAM) memory for data storage.

E) DX:- It is the data register.It has two parts DH and DL.This register is used in input/output addressing,Multiplication etc.

F) WRITE:-Memory unit supports two basic operations:- read and write. The write operation requires specification of the data to be written.Write operation stores a new value in memory.Operation require a memory address.

Steps in a Write Cycle:

1. Place the address of the location to be written on the address bus,

2. Place the data to be written on the data bus,

3. Activate the memory write control signal on the control bus,

4. Wait for the memory to store the data at the addressed location,

5. Drop the memory write signal to terminate the write cycle.