Lecture 5

Lecture 5

 

• Syscall
  
  • Used for input / output
    
  • Very primitive
    
  • Unique to system
    
  • Spim on unix
    
  • See text appendix A48 and the lesson number one
    
  • Invoked using syscall
    
  • $v0 will contain the service number (there are 10 services)
    
  • $a0..$a3 arguments
    
  • Print integer service number n = 1
    
• Multiply In MIPS
  
  • mult rs, rt
    
• Division in MIPS
  
  • div rs, rt
    
    • rs/rt
      
• Structured loops
  
  • While (save[i] == k ) i = i+j
    
    • Loop in MIPS
      

1. Get address of save[i]
   
2. Load save[i]
   
3. Go to exit if save != k
   
4. I ß i+ j increment i
   
5. Go to loop
   

• Loop    
  

Add $t1, $s3, $s3

Add $t1, $t1, $t1

Lw $t0, 0($t1)

Bne $t0, $s5, exit

Add $s3, $s3, $s4

J loop

Exit:

 

 

 

 

 

 

• Branch less than
  
• Set on less than
  
  • Slt a, b, c
    
  • Set a to 1 when b < c
    
  • This was on the TEST we wrote TWO DAYS AGO. This guy needs a new job.