3.5. Memory-Management Services

The memory organization and layout associated with a 4.4BSD process is shown in Fig. 3.3. Each process begins execution with three memory segments, called text, data, and stack. The data segment is divided into initialized data and uninitialized data (also known as bss). The text is read-only and is normally shared by all processes executing the file, whereas the data and stack areas can be written by, and are private to, each process. The text and initialized data for the process are read from the executable file.

Figure 3.3. Layout of a UNIX process in memory and on disk.