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| -rw-r--r-- | mips.html.markdown | 49 |
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diff --git a/mips.html.markdown b/mips.html.markdown index 952cc551..1c857ba4 100644 --- a/mips.html.markdown +++ b/mips.html.markdown @@ -19,18 +19,47 @@ The MIPS (Microprocessor without Interlocked Pipeline Stages) Assembly language .data # Section where data is stored in memory (allocated in RAM), similar to variables in higher level languages # Declarations follow a ( label: .type value(s) ) form of declaration - hello_world .asciiz "Hello World\n" # Declare a null terminated string - num1: .word 42 # Integers are referred to as words (32 bit value) - arr1: .word 1, 2, 3, 4, 5 # Array of words - arr2: .byte 'a', 'b' # Array of chars (1 byte each) - buffer: .space 60 # Allocates space in the RAM (not cleared to 0) +hello_world .asciiz "Hello World\n" # Declare a null terminated string + num1: .word 42 # Integers are referred to as words (32 bit value) + arr1: .word 1, 2, 3, 4, 5 # Array of words + arr2: .byte 'a', 'b' # Array of chars (1 byte each) + buffer: .space 60 # Allocates space in the RAM (not cleared to 0) # Datatype sizes - _byte: .byte 'a' # 1 byte - _halfword: .half 53 # 2 bytes - _word: .word 3 # 4 bytes - _float: .float 3.14 # 4 bytes - _double: .double 7.0 # 8 bytes + _byte: .byte 'a' # 1 byte + _halfword: .half 53 # 2 bytes + _word: .word 3 # 4 bytes + _float: .float 3.14 # 4 bytes + _double: .double 7.0 # 8 bytes + .align 2 # Memory alignment of data, where number indicates byte alignment in powers of 2. (.align 2 represents word alignment since 2^2 = 4 bytes) + +.text # Section that contains instructions and program logic +.globl _main # Declares an instruction label as global, making it accessible to other files + + _main: # MIPS programs execute instructions sequentially, where this will be executed first + + # Let's print "hello world" + la $a0, hello_world # Load address of string stored in memory + li $v0, 4 # Load the syscall value (indicating type of functionality) + syscall # Perform the specified syscall with the given argument ($a0) + + # Registers (used to hold data during program execution) + # $t0 - $t9 # Temporary registers used for intermediate calculations inside subroutines (not saved across function calls) + # $s0 - $s7 # Saved registers where values are saved across subroutine calls. Typically saved in stack + # $a0 - $a3 # Argument registers for passing in arguments for subroutines + # $v0 - $v1 # Return registers for returning values to caller function + + # Types of load/store instructions + la $t0, label # Copy the address of a value in memory specified by the label into register $t0 + lw $t0, label # Copy a word value from memory + lw $t1, 4($s0) # Copy a word value from an address stored in a register with an offset of 4 bytes (addr + 4) + lb $t2, label # Copy a byte value to the lower order portion of the register $t2 + lb $t2, 0($s0) # Copy a byte value from the source address in $s0 with offset 0 + # Same idea with 'lh' for halfwords + + sw $t0, label # Store word value into memory address mapped by label + sw $t0, 8($s0) # Store word value into address specified in $s0 and offset of 8 bytes + # Same idea using 'sb' and 'sh' for bytes and halfwords. 'sa' does not exist ```
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