This volume details how to program a microprocessor in five chapters. The first two chapters demonstrate the three characteristics of ISA (Instruction Set Architecture, cf. § V1-3.5), which are: instruction encoding, addressing modes and the instruction set of a generic component. Then, additional notions linked to the instruction set and execution are discussed in the third chapter. This primarily involves the notion of illegal, invalid, reserved and trusted instructions, the notion of memory alignment, orthogonality and the symmetry of the instruction set, as well as the notion of pure, re-entrant and relocatable code. Then, the subjects of execution time, memory requirements, execution modes, portability and virtualization will be discussed. Finally, it ends with aspects that are very important in industry, their hardware and software compatibilities, how to measure execution performances and the criteria for choosing a microprocessor or MPU (MicroProcessor Unit). The last two chapters study two ways of altering execution flow. These are the concepts of the sub-program and interruption.

NOTE.– The choice has been made to write the names of registers in upper case in the text and figures but in lower case in assembly language, since the norm (IEEE 1985) does not specify which case to use. The name of the instructions is in lower case in the text and programs (MIPS (Microprocessor without Interlocked Pipeline Stages) style), sometimes also in upper case (Motorola or Arm^® style). Moreover, the examples given refer to current and older microprocessors and computer processors for the purposes of instruction. This chapter is not intended to be exhaustive. It mainly presents the functions of the first MPUs. It will be completed by the following two books. The instructions cited will be complemented by MPU documentation or in a specialist work.