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