Several words and phrases will be used often in ECE 291 and throughout this manual. You should learn their meanings. Only partial definitions are given here. A complete discussion of some words would require several pages of explanation.


American Standard Code for Information Interchange

This is the set of 8-bit codes (including a parity bit) assigned to all the keys on the keyboard, including upper/lower case, punctuation and other symbols, and special communication control characters. Within your program, characters received from the keyboard or sent to the display are encoded in ASCII, even numerical digits such as 5, whose ASCII code is 35 (hex). Note, however, that the direct signals between the PC and the keyboard or the display are generally encoded in non-ASCII forms special to their use. See the ASCII tables for a complete listing of ASCII codes.


The process of translating an assembly language program into machine code so it can be executed by the PC. This is done by an assembler (in our case, the Netwide Assembler, NASM). The file generated by this process is called an object file, and has the extension .OBJ.

Assembly Language

The language used for writing programs for the PCs in ECE 291. Assembly language is a low level language, just one step up from the computer's native language, machine code.



A logical grouping of files on a disk for the purpose of organizing files. Each directory can contain files and/or other directories, so a hierarchy of files and directories can be created.


Usually a 3.5 inch removable media. A double-sided, high density diskette can hold about 1.44 MB of information in magnetic patterns on the surface of the disk. (MB stands for MegaByte, which is approximately 1 million bytes). Each PC in the lab has one 3.5 inch disk drive. Historical note: These used to be called floppy disks, because of the earlier 5¼ inch diskettes, which had floppy paper casings instead of hard plastic.



The process of creating a file or changing the contents of a file. There are several text editors available in the lab, including gvim, EMACS, and EDIT.

Execution Time

The time at which the linked-together code is actually being executed by the computer (as opposed to assembly time, when the program is being translated into machine code).



A unit of information stored on a disk. Each file has a specification of the form filename.extension, where the filename identifies the file, and the 3-letter extension identifies the file type. Some standard extensions are:

.ASM assembler source file
.BAT DOS batch file
.COM executable program file
.EXE executable program file
.LIB library file
.LST list file
.OBJ object file


Listing File

An optional output file from the assembly process that shows how the assembly language program has been translated into object code. A listing file has the extension .LST.


The process of combining (i.e., linking together) the object code modules (object files) of previously assembled program elements into a complete, executable program. The elements linked together might consist of your program and library subroutines. The final executable file has the extension .EXE or .COM; it can be loaded into the memory of the computer and executed.


Object File

The file produced by an assembler in the translation of a source file. The object file contains the binary encoding of the instructions and information about global symbols. It must be combined with other object code modules to form executable code. Object files have the extension .OBJ.

Operating System

The control program that supervises and controlsthe operations of the computer system. The operating system in the lab is Windows 2000, but most of what we'll be using in ECE 291 is a precursor to Windows called DOS (Disk Operating System) that is emulated by Windows 2000 in the Command Prompt.



A device which prints text and/or graphics on paper. You can use the printers in the lab to produce hard copies of your programs and other files.


A message displayed at the beginning of a line by a program to request a response from the user. DOS prompts for commands with the current disk drive and directory name followed by an angle bracket (e.g., D:\MYFILES⟩).


Run Time

See: Execution Time


Source File

A file which contains a program written in assembly language. It is an input to the assembler. An assembly language source file usually has the extension .ASM.