The level-ISA3 language is machine language, sequences of 1’s and 0’s sometimes abbreviated to hexadecimal. Computer pioneers had to program in machine language, but they soon revolted against such an indignity. Memorizing the opcodes of the machine and having to continually refer to ASCII charts and hexadecimal tables to get their programs into binary was no fun. The assembly level was invented to relieve programmers of the tedium of programming in binary.
Chapter 4 describes the Pep/8 computer at level ISA3, the machine level. This chapter describes level Asmb5, the assembly level. Between these two levels lies the operating system. Remember that the purpose of levels of abstraction is to hide the details of the ...