1. Your first C and C++ programs
Professor Hugh C. Lauer CS-2303, System Programming Concepts
(Slides include materials from The C Programming Language, 2nd edition, by Kernighan and Ritchie, Absolute C++, by Walter Savitch, The C++ Programming Language, Special Edition, by Bjarne Stroustrup, and from C: How to Program, 5th and 6th editions, by Deitel and Deitel)
CS-2303, A-Term 2012
Your first C and C++ programs

2. Your first C and C++ programs
Your first C program /*
* helloWorld.c - "hello, world" program */
#include <stdio.h>
int main (void) {
printf(″Hello, World!\n″);
return 0; }
CS-2303, A-Term 2012
Your first C and C++ programs

3. Your first C program (continued)/*
* helloWorld.c - "hello, world" program */
#include <stdio.h>
int main (void) {
printf(″Hello, World!\n″);
return 0; }
A comment:–
Surrounded by /* and */ or
“//” to end of line
Same as in Java
CS-2303, A-Term 2012
Your first C and C++ programs

4. Your first C program (continued)/*
* helloWorld.c - "hello, world" program */
#include <stdio.h>
int main (void) {
printf(″Hello, World!\n″);
return 0; }
A function definition
Note:– by convention, operating system invokes function named “main” to start a program.
“main” must return zero if successful, otherwise some non-zero value so OS can recognize an error
CS-2303, A-Term 2012
Your first C and C++ programs

5. Your first C program (continued)/*
* helloWorld.c - "hello, world" program */
#include <stdio.h>
int main (void) {
printf(″Hello, World!\n″);
return 0; }
A function definition
Note:– by convention, operating system invokes function named “main” to start a program.
“main” must return zero if successful, otherwise some non-zero value so OS can recognize an error
(arguments to main to be discussed later in course)
CS-2303, A-Term 2012
Your first C and C++ programs

6. Your first C program (continued)/*
* helloWorld.c - "hello, world" program */
#include <stdio.h>
int main (void) {
printf(″Hello, World!\n″);
return 0; }
printf — A call to the C library function to format and print a string of text
See K & R §1.1, §1.2, §1.5.3, and §7.2
Question:– where is printf declared?
CS-2303, A-Term 2012
Your first C and C++ programs

7. Your first C program (continued)/*
* helloWorld.c - "hello, world" program */
#include <stdio.h>
int main (void) {
printf(″Hello, World!\n″);
return 0; }
 Answer:– In this file!
Major difference from Java
An “include file” in C or C++ (a.k.a. a “header file”) is a text file declaring a bunch of stuff that is provided elsewhere!
E.g., in libraries OR in other C programs (i.e., modules) that you create
Copied bodily into your program as first step of compilation!
CS-2303, A-Term 2012
Your first C and C++ programs

8. Your first C and C++ programs
Questions?
CS-2303, A-Term 2012
Your first C and C++ programs

9. Your first C and C++ programs
Your first C++ program
Note file extension
An “include” file (as in C)
// helloworld.cpp
#include <iostream>
int main(void) {
std::cout << ″Hello World!″ << std::endl;
return 0; }
A (static) object of the standard class ostream
which is a subclass of iostream
CS-2303, A-Term 2012
Your first C and C++ programs

10. Your first C++ program (continued)
// helloworld.cpp
#include <iostream>
int main(void) {
std::cout << ″Hello World!″ << std::endl;
return 0; }
Another left shift operator, applied to the constant endl (defined in iostream)
The left shift operator applied to an ostream object and a string constant
CS-2303, A-Term 2012
Your first C and C++ programs

11. Your first C++ program (continued)
// helloworld.cpp
#include <iostream>
int main(void) {
std::cout << ″Hello World!″ << std::endl;
return 0; }
The scope resolution operator
Provides access to names declared in a class
CS-2303, A-Term 2012
Your first C and C++ programs

12. Your first C and C++ programs
Questions?
CS-2303, A-Term 2012
Your first C and C++ programs

13. What happens to your code …
… after it has been compiled but before it runs?
CS-2303, A-Term 2012
Your first C and C++ programs

14. Code generator & optimizer
Compilation (part 1)
All part of gcc
HelloWorld.c
Preprocessor
 Modifies the source code
Creates internal data structure representing the program 
Language translator
Code generator & optimizer
 Generates machine code
HelloWorld.o
However, program is not yet ready to execute!
CS-2303, A-Term 2012
Your first C and C++ programs

15. Compilation (continued)
printf.c
printf.o
Code gen & opt.
Preprocessor
Translator
HelloWorld.c
HelloWorld.o
Code gen & opt.
Preprocessor
Translator
gcc
gcc
ar (i.e., archive)
Linker (part of gcc)
a.out (or file name of your command or program)
Library of .o files for common routines
Loader (part of OS)
Note: this topic is developed in greater detail in CS-2011
Memory
CS-2303, A-Term 2012
Your first C and C++ programs

16. Your first C and C++ programs
Questions?
CS-2303, A-Term 2012
Your first C and C++ programs

17. Laboratory Assignment #1
Wednesday, August 29 — Edit, compile, and run both “Hello, World!” programs
I.e., in C and C++
On CCC Linux
Use gcc for compiler
Also, write a short program to do a simple numerical calculation
Based on your knowledge of Java
If time, work on Programming Assignment #1
Due Friday, August 31
CS-2303, A-Term 2012
Your first C and C++ programs

18. Extra Laboratory Credit
IF you already know how to do the laboratory
AND
and IF you have already submitted the required solution to Turnin
you may earn extra laboratory credit by helping the TAs help others
Speak to the TAs to take advantage of this
CS-2303, A-Term 2012
Your first C and C++ programs

19. Your first C and C++ programs
Questions?
CS-2303, A-Term 2012
Your first C and C++ programs