CRENT370 Example Project

This repository serves as a skeleton project for developing IBM MVS 3.8j applications in C using the CRENT370 C library. It demonstrates the setup, coding, and build process for mainframe applications with modern cross-compilation tools.

Project Structure

• src/ - Source code files (.c)
• inc/ - Header files (.h)
• jcl/ - JCL templates for mainframe jobs
• contrib/ - Dependencies (CRENT370 SDK)

Sample Application

The project includes a simple sample application that demonstrates two types of output:

1. WTO-Greeting (Write to Operator) - Sends messages to the system console
2. TSO-Greeting - Displays output on the TSO terminal

Prerequisites

On the Host / Mainframe

• A host installation of CRENT370 (GitHub Releases)
• Project datasets with the following attributes:

OBJECT Dataset

NAME OF NEW DATA SET ==> 'USER.SAMPLE.OBJECT'         
        RECORD FORMAT ==> FB                              
LOGICAL RECORD LENGTH ==> 80                              
  PHYSICAL BLOCK SIZE ==> 3120                            
               VOLUME ==> PUB000                          
                 UNIT ==>                                 
ALLOCATION SPACE UNIT ==> T       ( T OR C OR B )         
PRIMARY SPACE QUANTITY ==> 600                             
SECONDARY SPACE QUANTITY ==> 10                              
NUMBER OF DIRECTORY BLOCKS ==> 100 

NCALIB Dataset

NAME OF NEW DATA SET ==> 'USER.SAMPLE.NCALIB'             
        RECORD FORMAT ==> U                                   
LOGICAL RECORD LENGTH ==> 0                                   
  PHYSICAL BLOCK SIZE ==> 15040                               
               VOLUME ==> PUB000                              
                 UNIT ==>                                     
ALLOCATION SPACE UNIT ==> T       ( T OR C OR B )             
PRIMARY SPACE QUANTITY ==> 600                                 
SECONDARY SPACE QUANTITY ==> 100                                 
NUMBER OF DIRECTORY BLOCKS ==> 200

LOAD Dataset

NAME OF NEW DATA SET ==> 'USER.SAMPLE.LOAD'          
       RECORD FORMAT ==> U                              
LOGICAL RECORD LENGTH ==> 19069                          
  PHYSICAL BLOCK SIZE ==> 19069                          
              VOLUME ==> PUB000                         
                UNIT ==>                                
ALLOCATION SPACE UNIT ==> T       ( T OR C OR B )        
PRIMARY SPACE QUANTITY ==> 139                            
SECONDARY SPACE QUANTITY ==> 1                              
NUMBER OF DIRECTORY BLOCKS ==> 10

On the Development System

• Cross-compiler: gccmvs or c2asm370
• CRENT370 header files: Included in the contrib folder of this project
• Additional Tools (to be completed)
  • mvsasm
  • another tool 1
  • another tool 2

Configuration

The build configuration can be adjusted in the Makefile. The most important parameter is:

PROJECT_HLQ := USER.SAMPLE

This sets the High-Level Qualifier for all project datasets.

You need to change the location of the host datasets in jcl/link.jcl, too.

Development Workflow & Build Process

The development and build process consists of these steps:

1. Create or edit source code in src/ and inc/

2. C to Assembler Conversion:

   make
   

   This command invokes gccmvs or c2asm370 to convert C code into assembler code. For each C file, a corresponding .s assembler file is generated.

3. Assembler Compilation: The mvsasm tool generates a JCL for each .s file and submits it for compilation on the mainframe system. The compiled objects are stored in the OBJECT dataset and then added to the NCALIB dataset.

4. Linking: After compiling all components, submit the link job:

   cat jcl/link.jcl | submit_jcl
   

   A template for this is available in jcl/link.jcl.

5. Execute the resulting load module on the mainframe

Resources

• CRENT370 Repository
• GCCMVS Cross Compiler

License

See LICENSE file.