CS 3841 Computer Organization Recitation LAB 1

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CS 3841 Computer Organization Recitation LAB 1

• Introduction and Tools

Li Xu (Lee)
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TA Contact Information

• Name Li Xu(Lee)
• Email lxu_at_cs.utsa.edu
• Office 3.02.07 cubicle 9
• Office hour TR 1000-1130 a.m
• Office phone [phone]

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Notice

• Sign up sheet at each recitation
• The grade of this course, CS 3841, will be the
  same as that of CS 3843 course. (Please refer the
  syllable of CS 3843 for more information.)

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Assembly Language

• Assembly Language
• Human-readable mnemonic symbolic language for the
  machine instruction.
• Example
• assembly language statement add t0,t1,t2
• machine instruction 0000 0001 0010 1011 1000
  0000 0010 0000
• Linker
• Combines object and library files into executable
  files

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Assembly language

• Used when
• Speed/size important (embedded systems)
• Recoding critical part
• Exploit specialized instructions
• No high-level language is available
• Drawbacks
• Machine-specific
• Longer code
• Hard to read

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Sample C Program

• void main()
• // This program prints the sum of A and B
• int A 2
• int B 3
• printf("d", AB)

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Sample assembly program

• .data Data segment
• A .word 2 A is an integer with a value of 2
• B .word 3 B is an integer with a value of 3
• .text Text Segment
• .globl main
• main this program prints the sum of A and B
• lw t0, A load the value of A into register
  t0
• lw v0, B load the value of B into register
  v0
• add a0, t0, v0 add t0 and v0 and load the
  result into a0
• li v0, 1 system call print the value of a0
• syscall
• li v0, 10 system call exit the program
• syscall

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MIPS

• MIPS
• Target machine
• RISC Architecture
• Load-Store Instruction Set (ISA)
• MIPS Assembly Language
• Fixed-length instruction 32 bits
• Arithmetic Instruction
• Performs only ONE operation
• Have three variables
• Instruction operands are registers (32)
• Register size 32 bits

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MIPS simulator

• SPIM
• Software Simulator for MIPS 32 architecture
• Reads and executes assembly language file
• Provides debugger and OS services
• Versions
• Spim
• Simplest
• Command-line-driven program
• Xspim
• X-windows environment for Unix and Linux
• PCspim
• Microsoft windows
• Installation
• http//www.cs.wisc.edu/larus/spim.html

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Using xspim

• Start xspim
• Type xspim at prompt
• Write assembly source program
• Use text editor not a word processor to create
  program file
• Load a program file into memory
• load file name
• Run the program at optional address
• run ltaddressgt
• Debug
• step ltNgt step the program for N insruction
• continue continue program execution without
  stepping
• print N print register N
• print address print contents of memory at
  address
• Show Console
• terminal -gt popup console
• Exit the simulator
• exit or quit

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spim example
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Registers
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MIPS System calls
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Using System calls

• Read integer
• li v0,5
• syscall v0 has the input value
• Write integer
• li v0,1
• syscall a0 has the value to be printed

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Using PCSpim

• Double-click PCSpim icon on the desktop.
• Click Start gt All Programs gt PCSpim

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Window Panes

• Control buttons
• Register Display
• shows the contents (bit patterns in hex) of
• All 32 general purpose registers
• floating point registers, and a few others
• Text segment
• Shows assembly language program source
• Machine instructions (bit patterns in hex)
• Addresses of their memory locations.
• Data segment
• MIPS memory that hold ordinary data
• data pushed onto a stack.
• Messages
• Messages from the simulator (often error messages)

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Control buttons

• Open
• Save log file
• Go (run)
• Break
• Breakpoints

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Exercise

• Run Text editor.
• Type the first sample code on the course web
  page.
• (http//www.cs.utsa.edu/yum/7sp_2733/course.html
  )
• Save the file as add_A_B.asm.
• Run spim and execute the add_A_B.asm

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Exercise

• PCSpim
• double click PCSpim to run it.
• help (or ?)
• load add_A_B.asm
• run
• check the result 5
• quit (or exit)
• spim
• print_symbols
• print_all_regs

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Exercise

• add_A_B.asm
• The program prints the sum of A and B.
• A 2, B 3, Result 5
• sum_integers.asm
• Read the input N and prints the sum of the
  integers from 1 to N.