![Function header
int main(void)
• Return type
– Integer according to ANSI C standard
• Return 0, for success
• Or better yet, return EXIT_SUCCESS
• Return non-zero, otherwise
• Name of function
• Argument types
– void means no arguments
– More later on (int argc, char *argv[])](https://image.slidesharecdn.com/flgbsje9rbeat45ssbdn-signature-91f77658bc948ec5a8dd1dcec04e37ca491feef9f5dec765599dcd7a59873a3d-poli-160512172820/85/Minimal-standard-c-program-2-320.jpg)
Minimal standard c program
- 1. Minimal standard C program int main(void) { return 0 ; }
- 2. Function header int main(void) • Return type – Integer according to ANSI C standard • Return 0, for success • Or better yet, return EXIT_SUCCESS • Return non-zero, otherwise • Name of function • Argument types – void means no arguments – More later on (int argc, char *argv[])
- 3. C block • Delimited by “curlies” – { } – Encloses C statements (more later) – Starts with variable declarations (more later) • C90 and C++ are more forgiving – Can be nested • Function code must be in a block
- 4. Minimal C program with I/O #include <stdio.h> int main(void) { printf("Hello Worldn") ; return 0 ; }
- 5. Standard libraries • C has many “standard” libraries – But they really aren’t part of the “language” • C preprocessor (cpp) – Processes lines starting with # • And some other things • #include <stdio.h> – Adds ~900 lines of code needed to use standard I/O – cpp -E prog.c • Shows what is added
- 6. Printing a line • printf("3 feet is 36 inchesn") ; – Writes a line to standard output • 3 built-in FILE’s of C – Standard output (stdout) • Normal terminal output – Standard error (stderr) • Terminal output for errors – Standard input (stdin) • Terminal input
- 7. Escape sequences Allows inclusion of special characters n New line t Horizontal tab r Line feed ' Single quote " Double quote Backslash And a few more….
- 8. Formatted I/O • Allows the pretty printing of variable data – Easy to get started – But it takes time to master • Inspired by FORTRAN I/O – So it enables printing of aligned tables • printf("Easy as %8.4fn", PI) ; – Easy as ____3.1416
- 9. Variables • Names and places for data • Global variables – Declared outside of blocks • Local variables – Declared at beginning of blocks • In K&R and ANSI C – Stored on the stack
- 10. Variable names • Can contain – Letters (upper and lower) – Digits – Underscore • Cannot start with a digit • Cannot be a keyword – Like return
- 11. Variable declarations • Type in C – Integer, floating point, character, … – Determines space needed for variable – Determines what kind of add to do • Integer or IEEE floating? • Declaration statements – int lengthInFeet ; – int x, y, Y, z ;
- 12. Assignment statements • Gives a value to a variable – variable = expression ; • For our example int feet, inches ; feet = 10 ; inches = 12*feet ;
- 13. The whole program #include <stdio.h> int main(void) { int feet, inches ; feet = 5 ; inches = 12*feet ; printf("% d feet is %d inchesn", feet, inches) ; return 0 ; }
- 14. Things that go wrong • Syntactic error – Your program isn’t in legal C • inches = 12 feet ; • Semantic error – Your program has a bug • inches = feet/12 ;
- 15. Debuggers • Programs to “step” through your code • Linux gcc has gdb – Must compile with debugging symbols • gcc -g …….. – Many features • Set breakpoint • Examine variables – Hard to master • But worth the effort to learn a little
- 16. Phases • Compiling – Preprocessor • Expands #include statements – Lexical analysis • Finds the tokens (or words) – Syntactic analysis • Finds the expressions, statements, blocks, etc. – Code generation • Linking – Adds in the library routines • Loading – Processes DLL’s and relocation (if needed)