COMPUTER ASSEMBLY LANGUAGE Array Maximum and Minimum Declare an array of integer

Question

COMPUTER ASSEMBLY LANGUAGE

Array Maximum and Minimum

Declare an array of integers:

.data

size: .word 8

array: .word 23, -12, 45, -32, 52, -72, 8, 13

Write a program that determines the minimum and the maximum element in the array. Assume that the array has at least one element (in which case, that element will be both the minimum and maximum.) Leave the results in registers.

Qtspim simulator: The starting address of Data Section is 0x10000000

Mars simulator: The starting address of Data Section is 0x10010000

Explanation / Answer

Explanation :

In this Assembly Language Programming, A single program is divided into four Segments which are 1. Data Segment, 2. Code Segment, 3. Stack Segment, and 4. Extra Segment. Now, from these one is compulsory i.e. Code Segment if at all you don’t need variable(s) for your program.if you need variable(s) for your program you will need two Segments i.e. Code Segment and Data Segment.

Next Line –CODE SEGMENT

CODE SEGMENT is the starting point of the Code Segment in a Program and CODE is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can write the coding of the program.

Next Line –     ASSUME DS:DATA CS:CODE

In this Assembly Language Programming, their are Different Registers present for Different Purpose So we have to assume DATA is the name given to Data Segment register and CODE is the name given to Code Segment register (SS,ES are used in the same way as CS,DS )

Next Line – START:

START is the label used to show the starting point of the code which is written in the Code Segment. : is used to define a label as in C programming.

Next Line – MOV AX,DATA
MOV DS,AX

After Assuming DATA and CODE Segment, Still it is compulsory to initialize Data Segment to DS register. MOV is a keyword to move the second element into the first element. But we cannot move DATA Directly to DS due to MOV commands restriction, Hence we move DATA to AX and then from AX to DS. AX is the first and most important register in the ALU unit. This part is also called INITIALIZATION OF DATA SEGMENT and It is important so that the Data elements or variables in the DATA Segment are made accessable. Other Segments are not needed to be initialized, Only assuming is enhalf.

Next Line – LEA SI,ARR

LEA SI,ARR in this LEA stands for LOAD EFFECTIVE ADDRESS and it loads the effective address of second element into the first element. This same code can be interchangably written as MOV DX, OFFSET PRICE where OFFSET means effective address and MOV means move  second element into the first element. Here Base Address of variable PRICE is loaded in DX register.

Next Line – MOV AL,ARR[SI]
MOV LARGE,AL

MOV AL,ARR[SI] means move value of Array ARR in index of SI register to AL register. MOV LARGE,AL is to move AL register (First value in Array) to LARGE variable as we want to compare it with All the Array elements.

Next Line – MOV CX,LEN

MOV CX,LEN is used to move or assign value 8 (Length of Array) to CX. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – REPEAT:

REPEAT: is a LABEL and all the words ending in colon (:).

Next Line – MOV AL,ARR[SI]

MOV AL,ARR[SI] is to move value of Array ARR in index of SI register to AL register (Different values in Array). As we want to compare All elements with variable LARGE.

Next Line – CMP LARGE,AL
JG NOCHANGE

CMP LARGE,AL  is used to compare AX register with 9 and JG NOCHANGE jump if AL is greater to the respective LABEL NOCHANGE. The result of Comparision is not stored anywhere, but flags are set according to result. is Short Jump if first operand is Greater then second operand (as set by CMP instruction). Signed. SECOND is the label where the compiler will JUMP.

Next Line – MOV LARGE,AL

MOV LARGE,AL is to move AL register (larger value in Array) to LARGE variable.

Next Line – NOCHANGE:

NOCHANGE: is a LABEL and all the words ending in colon (:).

Next Line – INC SI

INC SI will increment the Address value present in SI register. Here we are using SI register as a SOURCE INDEX which holds the Address of Array elements to Cover all the elements in Array.

Next Line – LOOP REPEAT

LOOP REPEAT  This end of loop. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – EXIT: MOV AH,4CH
INT 21H

The above two line code is used to exit to dos or exit to operating system. Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 4ch, That means Return to Operating System or DOS which is the End of the program.

Next Line – CODE ENDS

CODE ENDS is the End point of the Code Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Code Segment.

Last Line – END START

END START is the end of the label used to show the ending point of the code which is written in the Code Segment.

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