This chapter discusses how statements can be organized into different kinds of blocks to form a PL/I program, how control flows among blocks, and how different blocks can make use of the same data.
Proper division of a program into blocks simplifies the writing and testing of the program, particularly when many programmers are writing it. Proper division can also result in more efficient use of storage, since automatic storage is allocated on entry to the block in which it is declared and released when the block is terminated.