programming
Statement: Exchange the contents of memory locations 2000H and 4000H
Program 1:
LDA 2000H : Get the contents of memory location 2000H into accumulator
MOV B, A : Save the contents into B register
LDA 4000H : Get the contents of memory location 4000Hinto accumulator
STA 2000H : Store the contents of accumulator at address 2000H
MOV A, B : Get the saved contents back into A register
STA 4000H : Store the contents of accumulator at address 4000H
Program 2:
LXI H 2000H : Initialize HL register pair as a pointer to memory location 2000H.
LXI D 4000H : Initialize DE register pair as a pointer to memory location 4000H.
MOV B, M : Get the contents of memory location 2000H into B register.
LDAX D : Get the contents of memory location 4000H into A register.
MOV M, A : Store the contents of A register into memory location 2000H.
MOV A, B : Copy the contents of B register into accumulator.
STAX D : Store the contents of A register into memory location 4000H.
HLT : Terminate program execution.
In Program 1, direct addressing instructions are used, whereas in Program 2, indirect addressing instructions are used.
Statement: Store the data byte 32H into memory location 4000H
Program 1:
MVI A, 52H : Store 32H in the accumulator
STA 4000H : Copy accumulator contents at address 4000H
HLT : Terminate program execution
Program 2:
LXI H : Load HL with 4000H
MVI M : Store 32H in memory location pointed by HL register pair (4000H)
HLT : Terminate program execution
The result of both programs will be the same. In program 1 direct addressing instruction is used, whereas in program 2 indirect addressing instruction is used.
Statement: Calculate the sum of series of numbers. The length of the series is in memory location 4200H and the series begins from memory location 4201H.
a. Consider the sum to be 8 bit number. So, ignore carries. Store the sum at memory location 4300H.
b. Consider the sum to be 16 bit number. Store the sum at memory locations 4300H and 4301H.
a. Sample problem
4200H = 04H
4201H = 10H
4202H = 45H
4203H = 33H
4204H = 22H
Result = 10 +41 + 30 + 12 = H
4300H = H
Source program:
LDA 4200H
MOV C, A : Initialize counter
SUB A : sum = 0
LXI H, 420lH : Initialize pointer
BACK: ADD M : SUM = SUM + data
INX H : increment pointer
DCR C : Decrement counter
JNZ BACK : if counter 0 repeat
STA 4300H : Store sum
HLT : Terminate program execution
b. Sample problem
4200H = 04H
420lH = 9AH
4202H = 52H
4203H = 89H
4204H = 3EH
Result = 9AH + 52H + 89H + 3EH = H
4300H = B3H Lower byte
4301H = 0lH Higher byte
Source program:
LDA 4200H
MOV C, A : Initialize counter
LXI H, 4201H : Initialize pointer
SUB A :Sum low = 0
MOV B, A : Sum high = 0
BACK: ADD M : Sum = sum + data
JNC SKIP
INR B : Add carry to MSB of SUM
SKIP: INX H : Increment pointer
DCR C : Decrement counter
JNZ BACK : Check if counter 0 repeat
STA 4300H : Store lower byte
MOV A, B
STA 4301H : Store higher byte
HLT :Terminate program execution
Statement: Multiply two 8-bit numbers stored in memory locations 2200H and 2201H by repetitive addition and store the result in memory locations 2300H and 2301H.
Sample problem:
(2200H) = 03H
(2201H) = B2H
Result = B2H + B2H + B2H = 216H
= 216H
(2300H) = 16H
(2301H) = 02H
Source program
LDA 2200H
MOV E, A
MVI D, 00 : Get the first number in DE register pair
LDA 2201H
MOV C, A : Initialize counter
LX I H, 0000 H : Result = 0
BACK: DAD D : Result = result + first number
DCR C : Decrement count
JNZ BACK : If count 0 repeat
SHLD 2300H : Store result
HLT : Terminate program execution
Statement:Divide 16 bit number stored in memory locations 2200H and 2201H by the 8 bit number stored at memory location 2202H. Store the quotient in memory locations 2300H and 2301H and remainder in memory locations 2302H and 2303H.
Sample problem
(2200H) = 60H
(2201H) = A0H
(2202H) = l2H
Result = A060H/12H = 8E8H Quotient and 10H remainder
(2300H) = E8H
(2301H) = 08H
(2302H= 10H
(2303H) 00H
Source program
LHLD 2200H : Get the dividend
LDA 2202H : Get the divisor
MOV C, A
LXI D, 0000H : Quotient = 0
BACK: MOV A, L
SUB C : Subtract divisor
MOV L, A : Save partial result
JNC SKIP : if CY 1 jump
DCR H : Subtract borrow of previous subtraction
SKIP: INX D : Increment quotient
MOV A, H
CPI, 00 : Check if dividend < divisor
JNZ BACK : if no repeat
MOV A, L
CMP C
JNC BACK
SHLD 2302H : Store the remainder
XCHG
SHLD 2300H : Store the quotient
HLT : Terminate program execution
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