{{Admon/tip|Australia and RedSPO600 Servers|Perform this lab on [[SPO600_ServersSPO600 Servers]] (you may use your own x86_64 system if desired, along with the AArch64 server).}} == Lab 4 ==

The code examples for this lab are available at this link: http:/in the file /england.proximity.on.ca/spo600public/spo600-lab4assembler-lab-examples.tgz Please download this archive to your accounts on the x86_64 and AArch64 systems, both [[SPO600 Servers|Aarchie and unpack the archive on both systems.Xerxes]]

|-- hello2.c # write() version |-- hello3.c # syscall () wrapper version |-- hello.c # printf () version

=== References Resources ===

*[[Syscalls]]* [[x86_64 Register and Instruction Quick Start]]** [[aarch64 Register and Instruction Quick Start]]

1. Build and run the two three C versions of the program for x86_64. Take a look at the differences in the code.

2. Review, build, Use the <code>objdump -d</code> command to dump (print) the object code (machine code) and disassemble it into assembler for each of the binaries. Find the <code><nowiki><main></nowiki></code> section and run take a look at the x86_64 assembly language programscode. Make sure you understand Notice the total amount of code.

43. Build Review, build, and run the C versions of the program for aarch64x86_64 assembly language programs. Verify that you can disassemble Take a look at the object code in the ELF binary using <code>objdump -d'''objectfile'''</code>and compare it to the source code. Notice the absence of other code (compared to the C binary, which had a lot of extra code).

4. Build and run the three C versions of the program for aarch64. Verify that you can disassemble the object code in the ELF binary using <code>objdump -d '''objectfile'''</code> and take a look at the code. 5. Review, build, and run the aarch64 assembly language programs. Make sure you understand Take a look at the code using <code>objdump -d '''objectfile'''</code> and compare it to the source code.

start = 0 /* starting value for the loop index ; '''note that this is a symbol (constant)''', not a variable */

/* '''... body of the loop ... do something useful here ... ''' */

Extend this This codedoesn't actually do anything while looping, combining because the body of the loop is empty. Combine it with code from the "Hello World" example, so that it prints a word each time it loops:  Loop Loop Loop Loop Loop Loop Loop Loop Loop Loop Then modify the message so that it includes the loop index values, showing each digit from 0 to 9 like this:

{{Admon/tip|Character conversion|In order to print the loop index value, you will need to convert from an integer to digit character. In ASCII/ISO-99598859-1/Unicode UTF-8, the digit characters are in the range 48-57 (0x30-0x39). You will also need to assemble the message to be printed for each line - you can do this by writing the digit into the message buffer before outputting it to stdout, which is probably the best approach, or you can perform a sequence of writes for the thee parts of the message ('Loop: ', number, '\n'). You may want to refer to the manpage for <code>ascii</code>.}}