---Constants---
For small constants (values between -32768 and 32767), we can use I-Type instructions as the value will fit in the immediate field. Remember that this field is signed (2's complement).

The format for I-Type instructions is [op-6bits][rs-5bits][rt-5bits][imm-16bits]

Examples:

C		int x = 20;

MIPS		addi $s0, $zero, 20

Machine Code	001000 00000 10000 0000 0000 0001 0100


C		int y = x | 301;

MIPS		andi $s1, $s0, 301

Machine Code	001100 10000 10001 0000 0001 0010 1101


For large constants (values greater than 32767 or smaller than -32678), we need to first load the value into a register before we can operate on it. This is a two step process that uses instructions lui (load upper immediate) and ori (bitwise OR immediate).

Examples:

C (One of the following, they all do the same thing)
		int y = 4000000;			     //base 10
		int y = 0b00000000001111010000100100000000;  //base 2, accepted by most compilers
		int y = 0x003d0900;			     //base 16

MIPS (Both of the following required to recreate the C step) 
		lui $s1, 61		#upper half of the base 2 number, converted to decimal		
		ori $s1, $s1, 2304	#lower half of the base 2 number, converted to decimal		

Machine Code
		001111 00000 10001 0000000000111101
		001101 10001 10001 0000100100000000


Step-by-Step:

lui step: 
	s1 = 61 << 16				
	s1 = 0000 0000 0011 1101 0000 0000 0000 0000  	#logical shift places 0s in lower half

ori step: s1 = s1 | 2304				#bitwise or


	0000 0000 0011 1101 0000 0000 0000 0000
|	0000 0000 0000 0000 0000 1001 0000 0000

=	0000 0000 0011 1101 0000 1001 0000 0000 


What about math?

C		int z = x + 4000000;

MIPS		lui $at, 61
		ori $at, $at, 2304
		add $s2, $s0, $at

---Addressing Modes---

MEMORY IS BYTE ADDRESSED AND WORD ALIGNED
(this is why you see x4 or <<2 on address calculations)

From slide 105

bne $t0, $s5, 2		#branch to 2 instructions further than the next instr
PC = PC + 4		always add 4 to PC
IF !t0 == s5 		also add "branch target address"
PC = PC + 2 << 2 

PC = 80012 + 4 + 2 << 2
PC = 80012 + 4 + 8
PC = 80012 + 12
PC = 80024