You can use the <return> key to split long constraints, and ILOG CPLEX still interprets the multiple lines as a single constraint. When you split a constraint in this way, do not press <return> in the middle of a variable name or coefficient. The following is acceptable:

time: -x1 + x2 + <return> x3 <= 20 <return> labor: x1 - 3x2 + x3 <= 30 <return>

The entry below, however, is incorrect since the <return> key splits a variable name.

time: -x1 + x2 + x <return> 3 <= 20 <return> labor: x1 - 3x2 + x3 <= 30 <return>

If you type a line that ILOG CPLEX cannot interpret, a message describing the problem will appear, and the entire line will be ignored. You must then re-enter the line.

The final thing to remember when you are entering a problem is that once you have pressed <return>, you can no longer directly edit the characters that precede the <return>. As long as you have not pressed the <return> key, you can use the <backspace> key to go back and change what you typed on that line. Once <return> has been pressed, the change command must be used to modify the problem. The change command is described in Changing a Problem on page 56.