On the Capabilities of While, Repeat, and Exit Statements

A well-formed program is defined as a program
in which loops and if statements are properly 
nested and can be entered only at their beginning.  A
corresponding definition is given for a well-formed 
flowchart.  It is shown that a program is well formed if
and only if it can be written with if, repeat, 
and multi-level exit statements for sequence control. 
It is also shown that if,while, and repeat statements 
with single-level exit do not suffice.  It is also shown
that any flowcharts can be converted to a well-formed 
flowchart by node splitting.  Practical implications are discussed.

CACM August, 1973

Peterson, W. W.
Kasami, T.
Tokura, N.

well-formed program, while statement, repeat statement,
exit statement, go to statement, flowchart, 
node splitting, software reliability

4.39 4.49 5.29

CA730818 JB January 23, 1978  10:20 AM

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