CSE 2541 – Advanced C Programming

1. CSE 2541 – Advanced C Programming Instructor: Matt Boggus boggus@cse.ohio-state.edu

2. Course info • Prereq – CSE 2221 or CSE 222 • Co-req – CSE 2231 • Website – http://www.cse.ohio-state.edu/~boggus/2541.html

3. Brief history of C • 1970’s • Unix • C, from BCPL (Thompson and Ritchie) • C programming Language • Widely used like the others: Fortran, Pascal • Main form of language for system programming • Available on any machine with C compiler and library

4. Why C? • Popular language • Operating systems (Win, Linux, FreeBSD) • Web servers (Apache) • Web browsers (Fox) • Mail servers (sendmail, postfix) • DNS servers (bind) • Graphics card programming (OpenCL) • Programming language rankings • Why? • Performance • Portability • Familiar to programmers

5. Why C? • Compared to assembly language • Abstracts the hardware view (registers, memory, call stacks), making code portable and easier • Provides variables, functions, arrays, complex arithmetic, Boolean expressions • Compared to other high-level languages • Maps almost directly into hardware instructions, making optimization easier • Provides a minimal set of abstractions compared to other HLLs • Like other HLLs, makes complex programming simpler (at the expense of efficiency)

6. C characteristics • "C" because many features came from earlier language “B“ • Reduced form of Basic Combined Programming Language, 1966 • Block structured • Blocks are denoted { } • Many utility functions provided in libraries • Libc, libpthread, libm • Nowhere near the functionality of other runtime environments • Some major C features • Functions, Structures, Types • Pointers – direct access to memory space

7. C vs. Java • Speed • Portability • Object orientation

8. C vs. Java • Pointers to memory • Platform dependent types • Programmer allocated memory • Declare variables at start of block • References to objects • Types have well defined sizes • Automatic garbage collection • Declare variable anywhere

9. Hello World – code /* Hello World! */ #include <stdio.h> int main() { printf(“Hello World!\n”); return 0; }

10. C compilation model

11. Hello World – walkthrough • C program: hello.c • emacs, vi, vim, pico, joe … • Plaintext only • Preprocessing: hello.s, assembly code • cc -S hello.c • Compilation: hello.o, a binary file • cc -c hello.s • Linking: a.out or hello, an executable file • cc hello.o • cc -o hello hello.o • Loading (dynamical linking) and execution: ./hello • ./a.out • ./hello

12. Hello World – content breakdown • Comment • Preprocessor directive • Function definition • Output statement • Return clause

13. Second Example #include <stdio.h> int main() { int first, second, add; float divide; printf("Enter two integers\n"); scanf("%d%d", &first, &second); add = first + second; divide = first / (float)second; printf("Sum = %d\n",add); printf("Division = %.2f\n",divide); return 0; }

14. Second example – content breakdown • Variables • Function calls • Input • Output • Operators • Typecasting