{"id":1670,"date":"2023-08-24T12:00:00","date_gmt":"2023-08-24T06:30:00","guid":{"rendered":"https:\/\/zmainframes.com\/zlog\/?p=1670"},"modified":"2023-08-21T15:38:57","modified_gmt":"2023-08-21T10:08:57","slug":"debugging-an-ibm-high-level-assembler-hlasm-program","status":"publish","type":"post","link":"https:\/\/zmainframes.com\/zlog\/debugging-an-ibm-high-level-assembler-hlasm-program\/","title":{"rendered":"Debugging an IBM High Level Assembler (HLASM) program."},"content":{"rendered":"
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Debugging an IBM High Level Assembler (HLASM) program involves systematically identifying and correcting errors in your code. Here’s a step-by-step method and instructions you can follow to debug an assembler program:<\/p>\n

Step 1: Prepare the Environment<\/strong><\/p>\n

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  1. Ensure that you have access to an IBM mainframe or emulator that supports HLASM.<\/li>\n
  2. Set up the necessary tools for editing, assembling, and debugging the program. Popular tools include TSO\/ISPF, TSO\/E, or an integrated development environment (IDE) like Compuware’s Xpediter.<\/li>\n<\/ol>\n

    Step 2: Review the Source Code<\/strong><\/p>\n

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    1. Open the source code of your HLASM program using your preferred editor.<\/li>\n
    2. Carefully review the code to understand its logic and purpose.<\/li>\n<\/ol>\n

      Step 3: Assemble the Code<\/strong><\/p>\n

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      1. Submit the HLASM source code for assembly using a JCL (Job Control Language) script.<\/li>\n
      2. Check the assembly output for any error messages or warnings. Address them before proceeding.<\/li>\n<\/ol>\n

        Step 4: Set Up Debugging<\/strong><\/p>\n

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        1. Determine the location of the program in memory (load address) after assembly.<\/li>\n
        2. Open the debugger (e.g., Xpediter) and specify the program load address.<\/li>\n<\/ol>\n

          Step 5: Start Debugging<\/strong><\/p>\n

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          1. Set breakpoints at the desired locations in your program using the debugger’s commands. This will pause execution at those points for analysis.<\/li>\n
          2. Start the debugging session and let the program run until a breakpoint is hit.<\/li>\n<\/ol>\n

            Step 6: Analyze Variables and Registers<\/strong><\/p>\n

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            1. At each breakpoint, inspect the contents of registers and memory locations. This can help identify incorrect values or data inconsistencies.<\/li>\n
            2. Compare the expected values with the actual values to pinpoint errors.<\/li>\n<\/ol>\n

              Step 7: Single-Step Execution<\/strong><\/p>\n

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              1. Use the debugger’s single-step or step-into command to execute the program one instruction at a time.<\/li>\n
              2. Observe the changes in registers, memory, and variables to track how the program is progressing.<\/li>\n<\/ol>\n

                Step 8: Monitor Program Flow<\/strong><\/p>\n

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                1. Continuously track the program’s flow to ensure it follows the expected logic.<\/li>\n
                2. Identify any unexpected branches, loops, or conditional statements that may lead to errors.<\/li>\n<\/ol>\n

                  Step 9: Investigate Abnormal Terminations<\/strong><\/p>\n

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                  1. If the program terminates abnormally (e.g., abend), review the error messages and codes provided by the debugger.<\/li>\n
                  2. Use these error messages to diagnose and rectify the issue.<\/li>\n<\/ol>\n

                    Step 10: Modify and Reassemble<\/strong><\/p>\n

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                    1. Make necessary code corrections based on your analysis during debugging.<\/li>\n
                    2. Assemble the corrected code again and repeat the debugging process if needed.<\/li>\n<\/ol>\n

                      Step 11: Test Corner Cases<\/strong><\/p>\n

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                      1. Test your program with various input data to ensure it handles different scenarios correctly.<\/li>\n
                      2. Debug any issues that arise during these tests.<\/li>\n<\/ol>\n

                        Step 12: Document and Verify Fixes<\/strong><\/p>\n

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                        1. Keep detailed records of the debugging process, including identified issues, corrections, and test results.<\/li>\n
                        2. Verify that your program now executes as expected without errors.<\/li>\n<\/ol>\n

                          Remember, debugging is an iterative process. You might need to go back and forth through these steps until your program is error-free and functions correctly. Patience, thoroughness, and systematic analysis are key to successful debugging.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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                          So far we’ve considered that the programmer has access to debug tools like Xpediter, however, if you don’t have access to a specialized debugger like Xpediter, you can still debug an IBM HLASM program using manual techniques and tools available on the mainframe. Here’s a step-by-step method for debugging without Xpediter:<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
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                          Step 1: Review the Source Code<\/strong><\/p>\n

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                          1. Open the HLASM source code using your preferred text editor.<\/li>\n
                          2. Understand the logic and purpose of the program.<\/li>\n<\/ol>\n

                            Step 2: Assemble the Code<\/strong><\/p>\n

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                            1. Submit the HLASM source code for assembly using JCL or the appropriate command.<\/li>\n
                            2. Check the assembler listing output for any error messages or warnings. Address them before proceeding.<\/li>\n<\/ol>\n

                              Step 3: Set Up Debugging<\/strong><\/p>\n

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                              1. Determine the load address of the program after assembly.<\/li>\n
                              2. Identify key points in your code where you want to inspect registers, memory, or variables.<\/li>\n<\/ol>\n

                                Step 4: Insert Debugging Code<\/strong><\/p>\n

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                                1. Insert instructions to display or output relevant information during program execution. Common instructions include PRINT or DISPLAY macros to output data to the system log or terminal.<\/li>\n
                                2. Modify your program to include breakpoints or temporary stops to allow you to observe the program’s state.<\/li>\n<\/ol>\n

                                  Step 5: Start Debugging<\/strong><\/p>\n

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                                  1. Execute the program with the debugging instructions in place.<\/li>\n
                                  2. Monitor the output or logs to observe the behavior of the program.<\/li>\n<\/ol>\n

                                    Step 6: Analyze Variables and Registers<\/strong><\/p>\n

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                                    1. Inspect the output logs or terminal messages to view the contents of registers, memory locations, and variables at different points in the program.<\/li>\n
                                    2. Compare expected values with actual values to identify discrepancies.<\/li>\n<\/ol>\n

                                      Step 7: Single-Step Execution<\/strong><\/p>\n

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                                      1. Manually execute the program one instruction at a time, using the relevant debugger commands available on the mainframe.<\/li>\n
                                      2. Keep track of changes in registers, memory, and variables as you step through the code.<\/li>\n<\/ol>\n

                                        Step 8: Monitor Program Flow<\/strong><\/p>\n

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                                        1. Continuously track the program’s flow to ensure it follows the expected logic.<\/li>\n
                                        2. Identify any unexpected branches, loops, or conditional statements that may lead to errors.<\/li>\n<\/ol>\n

                                          Step 9: Investigate Abnormal Terminations<\/strong><\/p>\n

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                                          1. If the program terminates abnormally (e.g., abend), review the error messages and codes provided by the mainframe.<\/li>\n
                                          2. Use these error messages to diagnose and rectify the issue.<\/li>\n<\/ol>\n

                                            Step 10: Modify and Reassemble<\/strong><\/p>\n

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                                            1. Make necessary code corrections based on your analysis during debugging.<\/li>\n
                                            2. Assemble the corrected code again and repeat the debugging process if needed.<\/li>\n<\/ol>\n

                                              Step 11: Test Corner Cases<\/strong><\/p>\n

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                                              1. Test your program with various input data to ensure it handles different scenarios correctly.<\/li>\n
                                              2. Debug any issues that arise during these tests.<\/li>\n<\/ol>\n

                                                Step 12: Document and Verify Fixes<\/strong><\/p>\n

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                                                1. Keep detailed records of the debugging process, including identified issues, corrections, and test results.<\/li>\n
                                                2. Verify that your program now executes as expected without errors.<\/li>\n<\/ol>\n

                                                  While debugging without a specialized tool like Xpediter may require more manual effort, it’s still a feasible approach to identify and fix issues in your HLASM program.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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                                                  Syntax of PRINT or DISPLAY macros described above:<\/strong><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
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                                                  In IBM HLASM (High Level Assembler), there is no direct “PRINT” or “DISPLAY” macro like you might find in higher-level programming languages. Instead, you can use the DC<\/code> (Define Constant) macro to output text or data to the system log or terminal during program execution.<\/div>\n<\/div>\n
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                                                  Here’s an example of how you might use the DC<\/code> macro to achieve a similar effect to printing or displaying information:<\/p>\n

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                                                  PRINTMSG DC C'This is a debug message'
                                                  \n<\/code><\/div>\n<\/div>\n

                                                  In this example, the DC<\/code> macro is used to define a character constant (C<\/code>) named PRINTMSG<\/code> with the text “This is a debug message”. You can then include this instruction in your program at the desired location to output the message when the program is executed.<\/p>\n

                                                  However, keep in mind that using DC<\/code> macros for debugging purposes might not provide as detailed or interactive information as a specialized debugging tool like Xpediter. You would need to strategically place these DC<\/code> macros in your code to observe the program’s behavior and state at specific points.<\/p>\n

                                                  If you’re working on a mainframe environment, you might also have access to system commands or utilities that allow you to display information interactively during program execution.<\/p>\n

                                                  Remember that IBM HLASM has its own unique syntax and set of macros, so it’s important to refer to the IBM HLASM documentation or manuals for a comprehensive list of available macros and their usage.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

                                                  Debugging an IBM High Level Assembler (HLASM) program involves systematically identifying and correcting errors in your code. Here’s a step-by-step […]<\/p>\n","protected":false},"author":515,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[556],"class_list":["post-1670","post","type-post","status-publish","format-standard","hentry","category-mainframes","tag-debugging"],"amp_enabled":true,"rttpg_featured_image_url":null,"rttpg_author":{"display_name":"zMainframes","author_link":"https:\/\/zmainframes.com\/zlog\/author\/zmainframes\/"},"rttpg_comment":0,"rttpg_category":"Mainframes<\/a>","rttpg_excerpt":"Debugging an IBM High Level Assembler (HLASM) program involves systematically identifying and correcting errors in your code. Here’s a step-by-step […]","_links":{"self":[{"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/posts\/1670","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/users\/515"}],"replies":[{"embeddable":true,"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/comments?post=1670"}],"version-history":[{"count":2,"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/posts\/1670\/revisions"}],"predecessor-version":[{"id":1672,"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/posts\/1670\/revisions\/1672"}],"wp:attachment":[{"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/media?parent=1670"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/categories?post=1670"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zmainframes.com\/zlog\/wp-json\/wp\/v2\/tags?post=1670"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}