Assembly language programming by c programming
language using asm keyword questions, answers and explanation
(1) What will be
output of following c program?
#include<stdio.h>
int main()
asm{
mov ax,61;
mov bx,10;
add bx,ax;
}
printf("\n%d",_BX);
return 0;
}
Output: 71
Explanation:
ax and bx is
general purpose register. Statement mov ax, 61 means value 61 is
storing at register ax. Statement
add bx, ax mean addition of content of register bx i.e 10 and content of register ax i.e. 61 and result of addition is
storing at register bx.
(2) What will be
output of following c program?
#include<stdio.h>
int main()
asm{
mov ax,10;
mov bx,20;
mov cx,30;
add ax,bx;
sub ax,cx;
}
printf("%d",_AX);
return 0;
}
Output: 0
Explanation:
Same concept as
in question 1
Mnemonic sub
means subtraction.
(3) What will be
output of following c program?
#include<stdio.h>
int main()
asm{
mov ax,10;
mov bx,20;
mov cx,30;
add ax,bx;
add bx,cx
}
printf("%d %d %d",_AX,_BX,_CX);
return 0;
}
Output: 30 50 30
Explanation:
same concept as in question 1.
(4) What will be
output of following c program?
#include<stdio.h>
int main()
asm{
mov ax,10;
mov cx,20;
inc cx;
div 2;
}
printf("%d ",_AX);
return 0;
}
Output: Compile
time error
Explanation:
Mnemonic in c
means increment content of register by one. Mnemonic div means division with ax. Operand of div must be a register not a value.
Note. Register ax is
known as accumulator.
(5) What will be
output of following c program?
#include<stdio.h>
int main()
asm{
mov ax,15;
mov cx,12;
mov bx,3;
div bx;
}
printf("%d ",_AX);
return 0;
}
Output: 5
Explanation:
Mnemonic div
means division of its operand with content of accumulator i.e. ax. Meaning of div bx means 15/3.
(6) What will be
output of following c program?
#include<stdio.h>
int main()
asm{
mov ax,15;
mov bx,3;
inc bx;
mul bx;
}
printf("%d ",_AX);
return 0;
}
Output: 60
Explanation:
Mnemonic mul
means multiplication of its operand with content of accumulator i.e. ax. Meaning of mul bx means 15*4.
Note: inc bx
means increase the content of register bx by one.
(7) What will be
output of following c program?
#include<stdio.h>=
int main()
int i=0;
asm mov dx,25;
for(i=0;i<5;i++)
asm dec dx;
printf("%d
",_DX);
return 0;
}
Output: 20
Explanation:
dec dx means
decrease the content of register dx by one.
(8) What will be
output of following c program?
#include<stdio.h>
int main()
int j=5;
asm mov cx,10;
asm OR cx,j;
printf("%d
",_CX);
return 0;
}
Output: 5
Explanation:
Mnemonic or
means bitwise OR operations between its operands.
(9) What will be
output of following c program?
#include<stdio.h>
int main()
asm {
mov ax,15;
mov dx,2;
and dx,ax;
not ax;
}
printf("%d %d
",_AX,_DX);
return 0;
}
Output: -16 2
Explanation:
Mnemonic and
means bitwise AND operations between its operands.
(10) What will
be output of following c program?
#include<stdio.h>
int main()
asm mov ax,15;
asm mov bx,5;
india:
asm inc ax;
asm dec bx;
asm jnz india;
printf("%d
",_AX);
return 0;
}
Output: 20
Explanation:
Statement jnz
India means jump to label india till content of last register i.e. bx is not zero. When content of register bx became zero then stop the jumping.
(11) What will
be output of following c program?
#include<stdio.h>
int main()
asm mov ax,15;
asm mov bx,1;
india:
asm xor ax,5;
asm dec bx;
asm jz india;
printf("%d
",_AX);
return 0;
}
Output: 15
Explanation:
Statement jz
India means jump to label india till content of last register i.e. bx is zero. When content of register bx became not zero then stop the
jumping.
(12) Write an
assembly language program in c program to find out factorial of given number?
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