Instructions for LINDO

Note: The instructions in this guide will not show you in great detail how to use specific LINDO commands or how to write programs. Consult the LINDO User's Manual for that purpose.

The objective of this Guide is to show you how to

1. Gain access to the LINDO program,

2. Enter a simple sample problem,

3. Save programs on a disk,

4. Retrieve programs previously saved, and

5. Print a program formulation or solution.

Start the LINDO program by going to the disk drive where the software is stored and typing LINDO. When the program responds with a colon (:) and a flashing cursor, you can enter specific LINDO commands. Try the following sample problem.

Sample problem

Use the data from HL12-35. The following information about Johnson Company's two products is provided:

                                                                                  
                            Contribution      Type A machine     Type B machine   
                               margin                                             


Product X                       $12              6 hours            4 hours       


Product Y                        $7              9 hours            5 hours       


Maximum hours available                         120 hours           80 hours      

Inputting and running the problem:

At the colon (:) type the objective function for this problem:

Max 12X + 7Y (Hit return key)

After the objective function type ST (Hit return key) which stands for subject to. At this point the cursor changes to a question mark (?). At the question mark, type the constraints:

6X + 9Y < 120 (Hit return key)

4X + 5Y < 80 (Hit return key)

(Note: LINDO interprets < to represent < and > to represent >.)

After the last constraint, type END (Hit return key) and the colon (:) should reappear. Type GO (Hit return key) and LINDO will show the first section of output for the problem. At this point DO RANGE (SENSITIVITY) ANALYSIS? will be displayed on the screen. Type Y (Hit return key). At the colon (:) type TABLE (Hit return key) to see the final tableau for the problem.

Reviewing, altering and rerunning the problem:

To review the objective function and constraint equations type LOOK ALL (Hit return key). To alter any element in a row, type ALT (Hit return key). LINDO will ask which row you want to alter (row 1 is the objective function and the constraints follow as rows 2 and 3, in this example). LINDO next asks for the variable you want to alter. Respond with either X or Y to alter the contribution margins in the objective function or the hours required to make one unit in either constraint. To alter the maximum hours available (the right hand side) in either constraint equation, type RHS. Next you simply type the new amount. Type GO (Hit return key) to obtain a solution to the problem with the new figures.

Saving and retrieving a problem:

To save a problem to a disk, type SAVE B:filename (Hit return key). The filename must be 8 or fewer characters long and begin with a letter. To retrieve a saved problem type RETR B:filename (Hit return key). If you don't know the filename, type RETR B: (Hit return key) to view a list of saved files on drive B:. Use the arrow keys to highlight the file you want to retrieve and hit the return key. The colon (:) will appear. Type GO (Hit return key) to run the problem.

Printing the solution:

The easiest way to print a solution is to divert the output to an ASCII file then load that file into a word processor (e.g. word perfect) and print from there. With the solution on the screen type DIVERT B:filename (Hit return key). Don't use the same filename that you used to save the problem above. Type LOOK ALL (Hit return key), GO (Hit return key), answer Y (Hit return key) to DO RANGE (SENSITIVITY) ANALYSIS? and type TABLE (Hit return key). The file containing the solution should be saved on the B: drive. Type RVRT (Hit return key) to revert to showing solutions on the screen (not saving them to filename).

Exiting LINDO:

Type QUIT (Hit return key) to exit LINDO.