C Programming in z/OS

(a 5-day course)

Course objectives
The C programming language was developped in 1972 by Dennis Ritchie at Bell Laboratories.
One of its first uses was in the rewriting of the UNIX operating system.
Strictly speaking, C is a system programming language. However, it is also useful for application programming.
On completion of this course, the students will know how to use all C functionalities, i.e. both the application and the system related ones.
Since C is implemented on a wide variety of systems, it is a multi-platform programming language available in UNIX as well as in non-UNIX environments.
Unfortunately, there are multiple C standards: Classic C (also known as Kernighan and Ritchie C), IBM's SAA C, Common Usage C (a.k.a. XPG3 C), ANSI C (a.k.a. ISO C), and POSIX.1 C.
On completion of this course, the students will know how to master the standard related issues.
C/370 is the generic name for the various C compilers for MVS, OS/390 and z/OS.
Our course covers the latest IBM C/370 compilers, i.e. "C for MVS/ESA", "OS/390 C" and "z/OS C" .
The course contents includes C/370 extensions such as record I/O and the use of Language Environment (LE).
Open Edition (OE) is a highly-reliable UNIX shell under MVS and OS/390. It is a MVS/SP4.3.0 feature that became an integral part of MVS beginning with MVS/SP5.1.0.
By the way: the official use of the name MVS ends with SP5.2.2 - the subsequent issue is known as OS/390 version 1 release 1 -, and the successor of OS/390 V1R10 is z/OS V1R1.
Beginning with OS/390 V2R6, OpenEdition is known as UNIX System Services ("USS").
USS allows UNIX programmers to develop new applications on the mainframe.
USS allows the porting of existing UNIX applications to the mainframe (server consolidation!).
USS is a prerequisite for Java, WebSphere Application Server, etc. in a OS/390 or z/OS environment.
The students will learn how to compile and execute C programs in MVS batch, under interactive TSO, and under the USS shell.
So, this course is also an introduction to USS and its facilities.
The students will learn how to access standard MVS data sets as well as UNIX files stored in the MVS Hierarchical File System (HFS).
When transporting a C application from one platform to another one, a lot (!) of problems arise from environment dependencies.
Our course covers the implementation of characters (EBCDIC versus ASCII), fixed-point integers, and floating-point numbers (S/370 "hexadecimal" floating-points versus IEEE "binary" formats), the differences between big-endian and little-endian computers, the maximum number of significant characters in an identifier, etc., etc.
C++ and JAVA are object oriented languages derived from C.
If you want to fully exploit all C++ and JAVA functionalities, you should master the fundamental (i.e. C language) Concepts.
Our course is both a C course for beginners and an advanced C course.

Audience
- OS/390-z/OS system programmers
- Senior programmers/analysts

Prerequisites
You need a working knowledge of the OS/390 or z/OS environment and you should have mastered at least one other programming language (e.g. COBOL or REXX).

Class infrastructure
The students must have access to an OS/390 or z/OS system and logon under TSO.

Course contents
Declaration versus definition
Trigraphs and escape sequences
Preprocessor directives
ASA files
The C compiler listing
The various C standards
Arithmetic types: integers, floating-points, and characters
Enumerations
Type conversion
Arithmetic, comparison, bitwise, logical and other operators
Signal handling
Operator precedence
Functions (including function prototyping)
Interlanguage communication (ILC)
Macros
Arrays
Pointers (including accessing system control blocks)
Complicated declarations
C versus REXX
if-else, switch, while, do-while, and for constructs
Conditional expressions
Recursivity and reentrancy
String, mathematical, utility, and other standard library functions
Passing arguments to the main function
Program execution under MVS batch, TSO, and OE
Text streams, binary streams, and record I/O
Standard streams and I/O redirection
File and terminal I/O
Structures, bit-fields, and unions
Using the Language Environment (LE)
Storage class specifiers
External linkage
Residency mode (RMODE) and Addressing mode (AMODE)
Dynamic allocation
C/MVS Multitasking Facility (MTF)
System C Programming (SPC) facilty
Dynamic Link Library (DLL) support
Memory files
Packed-decimal support
Traps and pitfalls