Computer Language : Usage of Syscall

Input / Output : Usage of Syscall

·         Assembly programs request a service by loading the system call (syscall) instruction.

Format  :

·        System services.

Service	System Call Code	Arguments	Result
print_int	1	$a0 = integer
print_float	2	$f12 = float
print_double	3	$f12 = double
print_string	4	$a0 = string
read_int	5		integer (in $v0)
read_float	6		float (in $f0)
read_double	7		double (in $f0)
read_string	8	$a0 = buffer, $a1 = length
sbrk	9	$a0 = amount	address (in $v0)
exit	10
print_character	11	$a0 = character
read_character	12		character (in $v0)
open	13	$a0 = filename,	file descriptor (in $v0)
		$a1 = flags, $a2 = mode
read	14	$a0 = file descriptor,	bytes read (in $v0)
		$a1 = buffer, $a2 = count
write	15	$a0 = file descriptor,	bytes written (in $v0)
		$a1 = buffer, $a2 = count
close	16	$a0 = file descriptor	0 (in $v0)
exit2	17	$a0 = value

Example :

a.) exit

b.) Get a number and store it

c. ) Print result from $t2

By : Wong Poh Ling    B031210033

Computer Language : Logical Operation

Logical Operation

Logical	and	and $1,$2,$3	$1 = $2 & $3	3 register operands; Logical AND
	or	or $1,$2,$3	$1 = $2 | $3	3 register operands; Logical OR
	not	nor $1,$1,$0	0=1/ 1=0	convert 1 to 0 convert 0 to 1
	and immediate	andi $1,$0,100	$1 = 100	Logical AND register, constant
	or immediate	ori $1,$0,100	$1 =100	Logical OR register, constant
	shift left logical	sll $1,$2,10	$1 = $2 << 10	Shift left by constant
	shift right logical	srl $1,$2,10	$1 = $2 >> 10	Shift right by constant

·         Example :   1.)                  sll   $t0,$t0,16                     srl   $t0,$t0,24

 0001 0010 0011 0100 0101 0110 0111 1000

solution : 

0101 0110 0111 1000 0000 0000 0000 0000      #sll

0000 0000 0000 0000 0000 0000 0101 0110      #srl

2.)         if     $t1 contains    00000000 00000000 00000000 00101100

                    $t2  contains   00000000 00000000 00000000 00001010

                What is the final content of $8 after this instruction is performed?

1.        and  $t0, $t1, $t2          # reg  $t0 = $t1 & $t2

2.        or   $t0, $t1, $t2          # reg  $t0 = $t1 & $t2

Solution:

For the AND operation, $t0 contains

      00000000 00000000 00000000 00001000

For the OR operation, $t0 contains

      00000000 00000000 00000000 00101110

By : Chong Cai Ning      B031210080

Computer Language : Arithmetic Operation

Arithmetic Operation

·         Arithmetic operations are performed on 32-bits numbers held in the general purpose registers (32-bit each)

·         Two types of instruction are included in this operation :

1.      Signed arithmetic : may generate an overflow

2.      Unsigned arithmetic : never generate an overflow

Category	Instruction	Example	Meaning
Arithmetic	add	add $1,$2,$3	$1 = $2 + $3
	add immediate	addi $1,$2,100	$1 = $2 + 100
	add unsigned	addu $1,$2,$3	$1 = $2 + $3
	add immediate unsigned	addi $1,$2,100	$1 = $2 + 100
	subtract	sub $1,$2,$3	$1 = $2 - $3
	subtract unsigned	subi $1,$2,$3	$1 = $2 - $3
	multiplication	mult $1,$2  mflo $3	$1*$2 quotient store in $3
	division	div $1,$2 mflo $3 mfhi $4	$1/$2 quotient store in $3 remainder store in $4

Example :

a.)    f = (g + h) - (i + j);                        #Assume f, g, h, i, j uses $s0, .. $s4

add $s0,$s1,$s2       # f = g + h

add $t0,$s3,$s4       # t0 = i + j

sub $s0,$s0,$t0       # f=(g+h)-(i+j)

b.)    a = c/d

a = c%d                                    #Assume a,b,c,d uses $s0…..$s4

div     $s2, $s3             # lo=c/d , hi=c%d

mflo  $s0                     #store quotient in $s0

mfhi  $s1                     #store remainder in $s1

By : Chong Lee Man   B031210367