Book excerpt: Computer Organization and Assembly Language Programming deals with lower level computer programming-machine or assembly language, and how these are used in the typical computer system. The book explains the operations of the computer at the machine language level. The text reviews basic computer operations, organization, and deals primarily with the MIX computer system. The book describes assembly language programming techniques, such as defining appropriate data structures, determining the information for input or output, and the flow of control within the program. The text explains basic I/O programming concepts, technique of interrupts, and an overlapped I/O. The text also describes the use of subroutines to reduce the number of codes that are repetitively written for the program. An assembler can translate a program from assembly language into a loader code for loading into the computer's memory for execution. A loader can be of several types such as absolute, relocatable, or a variation of the other two types. A linkage editor links various small segments into one large segment with an output format similar to an input format for easier program handling. The book also describes the use of other programming languages which can offer to the programmer the power of an assembly language by his using the syntax of a higher-level language. The book is intended as a textbook for a second course in computer programming, following the recommendations of the ACM Curriculum 68 for Course B2 "Computers and Programming.