MIPS程序设计实例

第一题：用系统功能调用实现简单输入输出

题目要求

利用系统功能调用从键盘输入，转换后在屏幕上显示，具体要求如下：

　　1、如果输入的是字母（A~Z，区分大小写）或数字（0~9），则将其转换成对应的英文单词后在屏幕上显示，对应关系见下表

　　2、若输入的不是字母或数字，则在屏幕上输出字符“*”

　　3、每输入一个字符，即时转换并在屏幕上显示

　　4、支持反复输入，直到按“?”键结束程序

MIPS代码

 .data
    alphabetU: .asciiz " Alpha\n"," Bravo\n"," China\n"," Delta\n"," Echo\n"," Foxtrot\n"," Golf\n"," Hotel\n",
         " India\n"," Juliet\n"," Kilo\n"," Lima\n"," Mary\n"," November\n"," Oscar\n"," Paper\n"," Quebec\n",
         " Research\n"," Sierra\n"," Tango\n"," Uniform\n"," Victor\n"," Whisky\n"," X-ray\n"," Yankee\n"," Zulu\n"
    alphabetL: .asciiz  " alpha\n"," bravo\n"," china\n"," delta\n"," echo\n"," foxtrot\n"," golf\n"," hotel\n"," india\n",
         " juliet\n"," kilo\n"," lima\n"," mary\n"," november\n"," oscar\n"," paper\n"," quebec\n"," research\n",
         " sierra\n"," tango\n"," uniform\n"," victor\n"," whisky\n"," x-ray\n"," yankee\n"," zulu\n"
    al_offset: .word ,,,,,,,,,,,,,,,,,,,,,,,,,
    number:  .asciiz  " Zero\n"," First\n"," Second\n"," Third\n"," Fourth\n"," Fifth\n"," Sixth\n"," Seventh\n"," Eighth\n"," Ninth\n"
    n_offset:  .word    ,,,,,,,,,
    exit_str: .asciiz "#Stop program#"

 .text
 .globl  main
 main:
     li $v0,                #$v0 contian character read
     syscall
     beq $v0,'?',exit         #if(v0 == '?'),exit

     #is symble?
     sub $t1,$v0,''
     blt $t1,,symble

     #is number?
     sub $t2,$t1,           #$t2 = $t1 -
     blt $t2,,getnum

     #is upper case?
     sub $t0,$v0,
     slt $s2,$t0,$      #if (v0 < 'Z') then s2 = 1
     sub $t0,$v0,
     sgt $s3,$t0,$      #if(v0 > 'A')  then  s3 = 1
     and $s1,$s2,$s3     #$s1 = ($s2 && s3)
     beq $s1,,getuword

     #is lower case?
     sub $t0,$v0,
     slt $s2,$t0,$      #if (v0 < 'Z') then s2 = 1
     sub $t0,$v0,
     sgt $s3,$t0,$      #if(v0 > 'A')  then  s3 = 1
     and $s1,$s2,$s3     #$s1 = ($s2 && s3)
     beq $s1,,getlword

 symble:
     li  $v0,
     add $a0,$,        #load value  into argument register $a0
     syscall              #print space

     add $a0,$a0,       # +  = '*'
     syscall 

     sub,$a0,$a0,        #'*' -  = '\n'
     syscall
     j main

 getnum:
     add $t2,$t2,        #add
     sll $t2,$t2,         #every word use  byte (no. at address of <<)

    la $s0,n_offset        #load address to $s0
    add $s0,$s0,$t2        #$s0 = $s0 + offset
    lw  $s1,($s0)  

    la $a0,number
    add $a0,$a0,$s1        #$a0 = number + offset
    li $v0,
    syscall
    j main

 getuword:
     sub,$t0,$t0,
     sll $t0,$t0,
     la $s0,al_offset
     add $s0,$s0,$t0
     lw  $s1,($s0)
     la $a0,alphabetU
     add $a0,$a0,$s1
     li $v0,
     syscall
     j main

 getlword:
     sub,$t0,$t0,
     sll $t0,$t0,
     la $s0,al_offset
     add $s0,$s0,$t0
     lw  $s1,($s0)
     la $a0,alphabetL
     add $a0,$a0,$s1
     li $v0,
     syscall
     j main

 exit:
     add $a0,$,'\n'
     li $v0,
     syscall

     la $a0,exit_str
     li $v0,
     syscall
     

第二题：字符串查找比较

题目要求

利用系统功能调用从键盘输入一个字符串，然后输入单个字符，查找该字符串中是否有该字符（区分大小写）。具体要求如下：

　　1、如果找到，则在屏幕上显示：

       Success! Location: X

　　　 其中，X为该字符在字符串中第一次出现的位置

　　2、如果没找到，则在屏幕上显示

　　　　Fail!

　　3、输入一个字符串后，可以反复输入希望查询的字符，直到按“?”键结束程序

　　4、每个输入字符独占一行，输出查找结果独占一行，位置编码从1开始。

提示：为避免歧义，字符串内不包含”?”符号

MIPS代码

 #https://ehye.github.io/2017/10/10/MIPS-program-design0/
 .data
     success_str: .asciiz  "\nSuccess! Location: "
     fail_str:  .asciiz  "\nFail!
     buffer: .space
     exit_str: .asciiz "\n#Stop program#"
    str1:  .asciiz "Enter string: "
    str2:  .asciiz "Enter char: 

 .text
 .globl  main
 main:
     #init
     # a0 = input/result string
    # a1 = input string length
    # a2 = input char
    # a3 = loop donefail
    li $a3,
    li $t0,

    #take string
    la $a0,buffer
    li $a1,
    li $v0,
    syscall

 takechar:
     li $v0,
     syscall
     beq $v0,'?',exit
     move  $a2,$v0

 search:
     beq $t0,$a1,fail       #if (i == length) then donefail
     la $a0,buffer                #else load byte
     add $t2,$a0,$t0            #$t2 = $a0 + offset
     lb  $s1,($t2)                #$s1 = *$t2
     beq $s1,$a2,success        #if($s1 == $a2),thne sucess
     add $t0,$t0,                #i++
     j search

 fail:
     add $a3,$zero,            # flag donefail =
     add $t0,$zero,$zero        # reset int i = 

     la $a0,fail_str
     li $v0,
     syscall

     add $a0,$zero,'\n'
     li $v0,
     syscall
     j takechar

 success:
     la $a0,success_str
     li $v0,
     syscall

     li $v0,
     add $a0,$t0,            #print index begin from
     syscall

     add $a0,$zero,'\n'
     li $v0,
     syscall
     add $t0,$zero,          #reset int i =
     j takechar

 exit:
     la  $a0,exit_str    #print exit
     li  $v0,
     syscall

     li  $v0,                #exit
     syscall

解释一下，由于这个编辑器插入代码不能选择MIPS，所以没有语法高亮，额，哎哎，水平太菜，知道好的解决方法得大佬请留言啊！