Assignment 5 Solution

Overview
In this assignment, you will rewrite the program you wrote in Assignment 4 using external subroutines instead of internal subroutines. There are a few minor changes and additional steps.

Input
The input to the program will be a file with an unknown number of records.
The data starts with a number of lines very much like those in the data for Assignment 4, followed by a line containing the integer -44444444. This number serves as a delimiter and is not part of the data. After that are three lines each containing two integers as described below.
Use the following JCL statement to specify the input file:
     //FT05F001  DD  DSN=KC02314.SUMMER18.CSCI360.HW5DATA,DISP=SHR
Otherwise the JCL is the same JCL we have been using.

What needs to be done
    • Call the BUILD subroutine to read lines in the file until it find the delimiter line. Each line contains zero or more integers. Put the integers in the table. Do not put the delimiter value -44444444 in the table.
    • After you find the line containing -44444444, end the BUILD subroutine and return to MAIN. Read the next three lines in the file. Each contains two small nonzero integers which we can call D1 and H1 (first line), D2 and H2 (second line) and D3 and H3 (third line). Store these in fullwords in MAIN for now.
    • In the main routine, print a heading saying something like "Table Contents".
    • Now call subroutine PRINT to print the contents of the table with 5 numbers on each line.
    • In the main routine, print a heading saying something like "Multiples of D1" (filling in the value of D1).
    • Call subroutine PRINT to print a list of all of the integers which are multiples of D1 with H1 values on each line. (The last line may not have as many as H1 values on it.)
    • Now repeat the last step with D2 and H2.
    • Now repeat the last step with D3 and H3.

External Subroutines
You will need several external subroutines:
    • BUILD is a subroutine that will read the input file and build the table. It will store the address of the last entry in a fullword passed in as its second parameter.
The arguments for BUILD are:
        ◦ the address of the input buffer
        ◦ the address of the table
        ◦ the address of a fullword containing the address of the next available entry
    • PRINT is a subroutine that will print all numbers in the table that are multiples of DIV (thus all the numbers if DIV is 1 or -1), with HOWMANY values per line, starting on a new page and double-spaced.
The arguments for PRINT are:
        ◦ the address of the table
        ◦ the address of a fullword containing the address of the next available entry
        ◦ the address of a fullword called DIV
        ◦ the address of a fullword called HOWMANY
The first time you call PRINT, use the values 1 and 5 for DIV and HOWMANY. Later, those values will come from input. Before you call PRINT, copy the values you want into DIV and HOWMANY. Another way to do this would be to have several parameter lists for PRINT, or to supply the parameter list as a literal.
There are several requirements for using an external subroutine:
    • Each external subroutine is actually a separate program. You need a CSECT with the name of the subroutine, as in:
     BUILD    CSECT
    • You need to create a parameter list for the subroutine (a set of consecutive fullwords, each containing the address of a parameter). We did this with internal subroutines.
    • You need to call the subroutine, as in:
     LA      1,BPARMS         Parmlist for BUILD
     L       15,=V(BUILD)     Get the address of BUILD  
     BALR    14,15            Branch to BUILD
Here the BALR instruction will set register 14 = the address of the next instruction after the BALR.
    • In the subroutine, you need a register save area and standard entry linkage. (You should probably go read about standard entry linkage.)
    • At the end of the subroutine, you need standard exit linkage. (You should probably go read about standard exit linkage.)

Other Requirements
    • You may assume that the table needs to hold no more than 75 values. You do not need to count the numbers. Each entry is one fullword. Initialize the table to the value -64 (as in 75F'-64').
    • In the PRINT subroutine, you may assume the value of HOWMANY is never more than 7.
    • In the PRINT subroutine, the value of DIV may be 1 or -1. If so, the subroutine will print all the numbers in the table. Everything is a multiple of 1 or -1.
    • The first time you call PRINT, the value of DIV should be 1 and the value of HOWMANY should be 5. The second time you call PRINT, the value of DIV should be D1 and the value of HOWMANY should be H1. The third time you call PRINT, use the values of D2 and H2 for DIV and HOWMANY, respectively. You can manage this with one parameter list containing the addresses of two fullwords, DIV and HOWMANY, and then change the values of those fullwords as needed.
    • In PRINT, double-space between lines of numbers.
    • You may use register equates if you want, but it is not required.
    • You may use extended mnemonics such as BH, BL, BNE, etc. for branch instructions.
    • Document your program as usual and submit it through Blackboard as usual.