The following guidelines are expected for all homework submissions:

Problems for Assignment #1

Learning Outcomes: 1) Verifying the development environment is set up properly for GitHub; 2) Verifying the development environment is set up and is functional for compiling C programs; 3) Verifying the development environment is set up and is functional for assembling nasm programs; 4) Verifying that the instructor can access the GitHub repository to provide feedback evaluations during the semester

This homework assignment simply extends the in-class assignment for week one. In classwork01 you set up and compiled a simple C program to make sure it worked. This proved the gcc compiler and linker is working on your computer. It also makes sure your editor is working properly so that you can create source code with it. These are basic steps, but I want to make sure everyone is on equal footing from the start of the semester.

The second part of this homework is to verify that your nasm assembler is working properly, which is also part of the classwork01 exercise.

Part One
  1. Add to your sayhello.c program from your week01.html in class exercise to prompt the user for their name from the terminal command line, using the printf() and the gets() functions. These are also demonstrated in the F to C conversion code on the week01.html page. Don't forget you will need to include BOTH the stdio.h and stdlib.h header files in your source file, just like you need to do in Java using the "import" keyword:

           #include <stdio.h>
           #include <stdlib.h>
           // main method and code go here...
  2. Add more lines to your program to change the Hello, World! message to say Hello, followed by the name that the user has input
  3. Compile and run your program to make sure everything works
  4. Test your program with several different inputs, like dog, $237.19, and just pressing enter without entering anything. See if you can break your program and make it crash!
  5. Go to GitHub and set up your repo and submission structure if you haven't already done so; make it look like the structure that is on the instructor's repo at this link.
  6. Upload and commit your completed sayhello.c file to your repo under the classwork/classwork01 folder.
  7. For a little extra challenge, see if you can dress up your program a bit by making it output some extra blank lines before and after the output. Can you make your program indent the output away from the left margin of the window?
  8. Commit all your code so far to your repo to make sure you've captured your properly working code.
Part Two
  1. Download and install the nasm assembler from this location using the version that is appropriate for your operating system. For MacOS, use the macosx version. You'll need to download the zip file and do the installation manually. Once that is done, verify that you can access it from your command line by running the command:


  2. Create a new file called sayhello.asm in the same directory where your sayhello.c is located.
  3. Edit the file and paste in the following code:
    Mac OS version [uses Mac system calls]
             global      start                   ; on Linux this should be "_start"
             section     .text
    start:   mov         rax, 0x02000004         ; system call for write [Linux should be "_start"]
             mov         rdi, 1                  ; file handle 1 is stdout
             mov         rsi, message            ; address of string to output
             mov         rdx, 13                 ; number of bytes
             syscall                             ; invoke operating system to do the write
             mov         rax, 0x02000001         ; system call for exit [Linux use "60"]
             xor         rdi, rdi                ; exit code 0
             syscall                             ; invoke operating system to exit
             section     .data
    message: db          "Hello, World", 10

    Windows version [uses C library's 'printf' function]
             global      _main                   ; declares the starting entry point
             extern      _printf                 ; we'll use the "C" library for now
             section .text                       ; code starts here
    _main:   push        message                 ; put the message on the stack
             call        _printf                 ; call "printf()" to display it
             add         esp, 4                  ; set up the exit
             ret                                 ; return to Windows
    message: db  "Hello, World!", 10, 0
  4. Assemble, link, and run with the following command:
    Mac OS version [updated]
          nasm -fmacho64 sayhello.asm && ld -macosx_version_min 10.7 sayhello.o -o sayhello && ./sayhello
    [NOTE: this is a different command than the original, using the linker instead of gcc] you can also use semicolons to separate commands:
    nasm -fmacho64 sayhello.asm;ld -macosx_version_min 10.7 sayhello.o -o sayhello;./sayhello note the semicolons ↑ ↑

    Windows version
          nasm -fwin32 sayhello.asm && gcc sayhello.obj -o sayhello.exe && sayhello
  5. NOTE that the last part of the commands shown above will run your program, but you can also run it by just entering that last part. On Mac, run using ./sayhello and on Windows run using sayhello. If there are errors, do some Internet searching to see if you can track down what's going on. If you can't get some help from your friendly prof or a TA from the Keck Lab in Discord.
  6. Now that you have both the C and nasm versions working, see if you can figure out how to do the same dressing up of your assembler code, putting extra blank lines before and after the text output. Feel free to search the Internet for help. [Hint: check the message label in the code for clues!]
  7. When everything is working, be sure to commit your code to your repo!