A Unifying Framework

In all programming environments, from the most rudimentary to the most advanced, it is possible to identify two distinct components, the program preparation component and the program execution component. On a bare machine, the program preparation component consists of the switches or push buttons by which programs and data may be entered into the memory of the machine; more advanced systems supplement this with text editors, compilers, assemblers, object library managers, linkers, and loaders. On a bare machine, the program execution component consists of the hardware of the machine, the central processors, any peripheral processors, and the various memory resources; more advanced systems supplement this with operating system services, libraries of predefined procedures, functions and objects, and interpreters of various kinds.
Within the program execution component of a programming environment, it is possible to distinguish between those facilities needed to support a single user process, and those which are introduced when resources are shared between processes. Among the facilities which may be used to support a single process environment are command language interpreters, input-output, file systems, storage allocation, and virtual memory. In a multiple process environment, processor allocation, interprocess communication, and resource protection may be needed. Figure 1.1 lists and classifies these components.
Editors
Compilers
Assemblers Program Preparation
Linkers
Loaders
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Command Languages
Sequential Input/Output
Random Access Input/Output
File Systems Used by a Single Process
Window Managers
Storage Allocation
Virtual Memory
------------------------------ Program Execution Support
Process Scheduling
Interprocess Communication
Resource Sharing Used by Multiple Processes
Protection Mechanisms
Figure 1.1. Components of a programming environment.
This text is divided into three basic parts based on the distinctions illustrated in Figure 1.1. The distinction between preparation and execution is the basis of the division between the first and second parts, while the distinction between single process and multiple process systems is the basis of the division between the second and third parts.