HLASM: V1R6 Language Ref

Chapter 1. IntroductionA computer can understand and interpret only machine language. Machinelanguage is in binary form and, thus, very difficult to write. The assemblerlanguage is a symbolic programming language that you can use to codeinstructions instead of coding in machine language.Because the assembler language lets you use meaningful symbols made up ofalphabetic and numeric characters, instead of just the binary digits 0 and 1 used inmachine language, you can make your coding easier to read, understand, andchange. The assembler must translate the symbolic assembler language intomachine language before the computer can run your program. The specificprocedures followed to do this may vary according to the system you are using.However, the method is basically the same for all systems:┌───────────────────┐│ Your assembler ││ language source ├─────┐│ statements │ │└───────────────────┘ │┌───────────┴───────────┐│ HIGH LEVEL ASSEMBLER │└─────────┬───┬─────────┘│ ││ │┌──────────┐ │ │ ┌──────────────────┐│ Messages │ │ │ │ Machine language ││ and ├◄───────────┘ └──────────►┤ version of your ││ listings │ │ program ││ . │ └─────────┬────────┘│ . │ │└────┬─────┘│││││ ┌─────────────────┐ ││ │ LINKER ├◄─────────────┘│└──────┬───┬──────┘│ │ ││ │ │ ┌───────────────────┐└──────────────────┘ └──────────►┤ Executable module │└───────────────────┘Figure 1. Assembling and link-editing your assembler language programYour program, written in the assembler language, becomes the source module thatis input to the assembler. The assembler processes your source module andproduces an object module in machine language (called object code). The objectmodule can be used as input to be processed by the linker or the binder. The linkeror binder produces a load module (z/OS and CMS), or a phase (z/VSE), that canbe loaded later into the main storage of the computer. When your program isloaded, it can then be run. Your source module and the object code produced areprinted, along with other information, on a program listing.© Copyright IBM Corp. 1982, 2008 3