Advanced C Programming
Course info •
Prereq – CSE 2221 or CSE 222
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Co-req – CSE 2231
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Brief history of C •
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1970’s –
Unix
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C, from BCPL (Thompson and Ritchie)
C programming Language –
Widely used like the others: Fortran, Pascal
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Main form of language for system programming
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Available on any machine with C compiler and library
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Popular language
Why C?
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Operating systems (Win, Linux, FreeBSD)
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Web servers (Apache)
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Web browsers (Fox)
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Mail servers (sendmail, postfix)
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DNS servers (bind)
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Graphics card programming (OpenCL)
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Programming language rankings
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Why? –
Performance
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Portability
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Familiar to programmers
Why C? •
Compared to assembly language –
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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 –
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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)
C characteristics •
"C" because many features came from earlier language “B“ –
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Block structured –
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Reduced form of Basic Combined Programming Language, 1966
Blocks are denoted { }
Many utility functions provided in libraries –
Libc, libpthread, libm
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Nowhere near the functionality of other runtime environments
Some major C features –
Functions, Structures, Types
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Pointers – direct access to memory space
C vs. Java
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Speed
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Portability
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Object orientation
C vs. Java •
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Pointers to memory Platform dependent types Programmer allocated memory Declare variables at start of block
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References to objects Types have well defined sizes Automatic garbage collection Declare variable anywhere
Hello World – code /* Hello World! */ #include <stdio.h> int main() { printf(“Hello World!\n”); return 0; }
C compilation model
Hello World – walkthrough
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C program: hello.c –
emacs, vi, vim, pico, joe …
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Plaintext only
Preprocessing: hello.s, assembly code –
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Compilation: hello.o, a binary file –
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cc -S hello.c cc -c hello.s
Linking: a.out or hello, an executable file –
cc hello.o
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cc -o hello hello.o
Loading (dynamical linking) and execution: ./hello
Hello World – content breakdown •
Comment
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Preprocessor directive
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Function definition
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Output statement
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Return clause
#include <stdio.h>
Second Example
int main() { int first, second, add; float divide; printf("Enter two integers\n"); scanf("%d%d", &first, &second);
Second example – content breakdown
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Variables
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Function calls –
Input
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Output
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Operators
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Typecasting