String Length

The length of a null-terminated string is defined as the number of characters it contains not counting the null. To calculate length, start the count at zero. Then increment the count for each successive non-null byte. When you hit the null, stop counting.

The structured flow chart shows this procedure. It describes the algorithm in general terms. Assembly language details are left to the coding stage. Here is an outline of the program:

 

## strlen.asm
##
## Count the characters in a string
##
## Registers:
## $8 -- count
## 

        .text
        .globl  main
		
# Initialize
main:    ori     $8,$0,0     #  count = 0

# while not ch==null do
loop:    . . . 
         . . .
         . . .
         
         j    loop
         sll   $0,$0,0       # branch delay slot
		 
# finish
done:    sll   $0,$0,0       # target for branch

         .data
string:  .asciiz  "Time is the ghost of space."