Brief Introduction to the C Programming Language : Brief Introduction to the C Programming Language Fred Kuhns
fredk@cse.wustl.edu
Applied Research Laboratory,
Department of Computer Science and Engineering,
Washington University in St. Louis
Introduction : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Introduction The C programming language was designed by Dennis Ritchie at Bell Laboratories in the early 1970s
Influenced by
ALGOL 60 (1960),
CPL (Cambridge, 1963),
BCPL (Martin Richard, 1967),
B (Ken Thompson, 1970)
Traditionally used for systems programming, though this may be changing in favor of C++
Traditional C:
The C Programming Language, by Brian Kernighan and Dennis Ritchie, 2nd Edition, Prentice Hall
Referred to as K&R
Standard C : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Standard C Standardized in 1989 by ANSI (American National Standards Institute) known as ANSI C
International standard (ISO) in 1990 which was adopted by ANSI and is known as C89
As part of the normal evolution process the standard was updated in 1995 (C95) and 1999 (C99)
C++ and C
C++ extends C to include support for Object Oriented Programming and other features that facilitate large software development projects
C is not strictly a subset of C++, but it is possible to write “Clean C” that conforms to both the C++ and C standards.
Elements of a C Program : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Elements of a C Program A C development environment includes
System libraries and headers: a set of standard libraries and their header files. For example see /usr/include and glibc.
Application Source: application source and header files
Compiler: converts source to object code for a specific platform
Linker: resolves external references and produces the executable module
User program structure
there must be one main function where execution begins when the program is run. This function is called main
int main (void) { ... },
int main (int argc, char *argv[]) { ... }
UNIX Systems have a 3rd way to define main(), though it is not POSIX.1 compliantint main (int argc, char *argv[], char *envp[])
additional local and external functions and variables
A Simple C Program : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab A Simple C Program Create example file: try.c
Compile using gcc:gcc –o try try.c
The standard C library libc is included automatically
Execute program./try
Note, I always specify an absolute path
Normal termination:void exit(int status);
calls functions registered with atexit()
flush output streams
close all open streams
return status value and control to host environment /* you generally want to
* include stdio.h and
* stdlib.h
* */
#include
#include
int main (void)
{
printf(“Hello World\n”);
exit(0);
}
Source and Header files : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Source and Header files Just as in C++, place related code within the same module (i.e. file).
Header files (*.h) export interface definitions
function prototypes, data types, macros, inline functions and other common declarations
Do not place source code (i.e. definitions) in the header file with a few exceptions.
inline’d code
class definitions
const definitions
C preprocessor (cpp) is used to insert common definitions into source files
There are other cool things you can do with the preprocessor
Another Example C Program : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Another Example C Program example.c /* this is a C-style comment
* You generally want to palce
* all file includes at start of file
* */
#include
#include
int
main (int argc, char **argv)
{
// this is a C++-style comment
// printf prototype in stdio.h
printf(“Hello, Prog name = %s\n”,
argv[0]);
exit(0);
} /* comments */
#ifndef _STDIO_H
#define _STDIO_H
... definitions and protoypes
#endif /usr/include/stdio.h /* prevents including file
* contents multiple
* times */
#ifndef _STDLIB_H
#define _STDLIB_H
... definitions and protoypes
#endif /usr/include/stdlib.h #include directs the preprocessor
to “include” the contents of the file
at this point in the source file.
#define directs preprocessor to define macros.
Passing Command Line Arguments : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Passing Command Line Arguments When you execute a program you can include arguments on the command line.
The run time environment will create an argument vector.
argv is the argument vector
argc is the number of arguments
Argument vector is an array of pointers to strings.
a string is an array of characters terminated by a binary 0 (NULL or ‘\0’).
argv[0] is always the program name, so argc is at least 1. ./try –g 2 fred argc = 4,
argv = ‘t’‘r’‘y’‘\0’ argv:
[0]
[1]
[2]
[3]
[4] NULL ‘-’‘g’‘\0’ ‘2’‘\0’ ‘f’‘r’‘e’‘d’‘\0’
C Standard Header Files you may want to use : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab C Standard Header Files you may want to use Standard Headers you should know about:
stdio.h – file and console (also a file) IO: perror, printf, open, close, read, write, scanf, etc.
stdlib.h - common utility functions: malloc, calloc, strtol, atoi, etc
string.h - string and byte manipulation: strlen, strcpy, strcat, memcpy, memset, etc.
ctype.h – character types: isalnum, isprint, isupport, tolower, etc.
errno.h – defines errno used for reporting system errors
math.h – math functions: ceil, exp, floor, sqrt, etc.
signal.h – signal handling facility: raise, signal, etc
stdint.h – standard integer: intN_t, uintN_t, etc
time.h – time related facility: asctime, clock, time_t, etc.
The Preprocessor : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab The Preprocessor The C preprocessor permits you to define simple macros that are evaluated and expanded prior to compilation.
Commands begin with a ‘#’. Abbreviated list:
#define : defines a macro
#undef : removes a macro definition
#include : insert text from file
#if : conditional based on value of expression
#ifdef : conditional based on whether macro defined
#ifndef : conditional based on whether macro is not defined
#else : alternative
#elif : conditional alternative
defined() : preprocessor function: 1 if name defined, else 0 #if defined(__NetBSD__)
Preprocessor: Macros : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Preprocessor: Macros Using macros as functions, exercise caution:
flawed example: #define mymult(a,b) a*b
Source: k = mymult(i-1, j+5);
Post preprocessing: k = i – 1 * j + 5;
better: #define mymult(a,b) (a)*(b)
Source: k = mymult(i-1, j+5);
Post preprocessing: k = (i – 1)*(j + 5);
Be careful of side effects, for example what if we did the following
Macro: #define mysq(a) (a)*(a)
flawed usage:
Source: k = mysq(i++)
Post preprocessing: k = (i++)*(i++)
Alternative is to use inline’ed functions
inline int mysq(int a) {return a*a};
mysq(i++) works as expected in this case.
Preprocessor: Conditional Compilation : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Preprocessor: Conditional Compilation Its generally better to use inline’ed functions
Typically you will use the preprocessor to define constants, perform conditional code inclusion, include header files or to create shortcuts
#define DEFAULT_SAMPLES 100
#ifdef __linux
static inline int64_t gettime(void) {...}
#elif defined(sun)
static inline int64_t gettime(void) {return (int64_t)gethrtime()}
#else
static inline int64_t gettime(void) {... gettimeofday()...}
#endif
Another Simple C Program : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Another Simple C Program int main (int argc, char **argv) {
int i;
printf(“There are %d arguments\n”, argc);
for (i = 0; i < argc; i++)
printf(“Arg %d = %s\n”, i, argv[i]);
return 0;
} Notice that the syntax is similar to Java
What’s new in the above simple program?
of course you will have to learn the new interfaces and utility functions defined by the C standard and UNIX
Pointers will give you the most trouble
Arrays and Pointers : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab A variable declared as an array represents a contiguous region of memory in which the array elements are stored.
int x[5]; // an array of 5 4-byte ints.
All arrays begin with an index of 0
An array identifier is equivalent to a pointer that references the first element of the array
int x[5], *ptr;ptr = &x[0] is equivalent to ptr = x;
Pointer arithmetic and arrays:
int x[5];x[2] is the same as *(x + 2), the compiler will assume you mean 2 objects beyond element x. Arrays and Pointers
Pointers : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Pointers For any type T, you may form a pointer type to T.
Pointers may reference a function or an object.
The value of a pointer is the address of the corresponding object or function
Examples: int *i; char *x; int (*myfunc)();
Pointer operators: * dereferences a pointer, & creates a pointer (reference to)
int i = 3; int *j = &i;*j = 4; printf(“i = %d\n”, i); // prints i = 4
int myfunc (int arg);int (*fptr)(int) = myfunc; i = fptr(4); // same as calling myfunc(4);
Generic pointers:
Traditional C used (char *)
Standard C uses (void *) – these can not be dereferenced or used in pointer arithmetic. So they help to reduce programming errors
Null pointers: use NULL or 0. It is a good idea to always initialize pointers to NULL.
Pointers in C (and C++) : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Pointers in C (and C++) Address 0x3dc 0x3d8 Program Memory 0x3cc 0x3c8 0x3c4 0x3c0 Note: The compiler converts z[1] or *(z+1) toValue at address (Address of z + sizeof(int));
In C you would write the byte address as:
(char *)z + sizeof(int);
or letting the compiler do the work for you
(int *)z + 1; Step 1:
int main (int argc, argv) {
int x = 4;
int *y = &x;
int *z[4] = {NULL, NULL, NULL, NULL};
int a[4] = {1, 2, 3, 4};
... 0x3bc 0x3b8 0x3b4 0x3b0 0x3d4 0x3d0 z[3] z[2] z[1] z[0] a[3] a[2] a[1] a[0] x y
Pointers Continued : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Pointers Continued 4 0x3dc Address 0x3dc 0x3d8 Program Memory 0x3bc 0x3b8 0x3b4 0x3b0 0x3cc 0x3c8 0x3c4 0x3c0 Step 1:
int main (int argc, argv) {
int x = 4;
int *y = &x;
int *z[4] = {NULL, NULL, NULL, NULL};
int a[4] = {1, 2, 3, 4};
Step 2: Assign addresses to array Z
z[0] = a; // same as &a[0];
z[1] = a + 1; // same as &a[1];
z[2] = a + 2; // same as &a[2];
z[3] = a + 3; // same as &a[3]; 0x3bc 0x3b8 0x3b4 0x3b0 4 3 2 1 NA 0x3d4 0x3d0 z[3] z[2] z[1] z[0] a[3] a[2] a[1] a[0] NA x y
Pointers Continued : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Pointers Continued 4 0x3dc Address 0x3dc 0x3d8 Program Memory 0x3bc 0x3b8 0x3b4 0x3b0 0x3cc 0x3c8 0x3c4 0x3c0 Step 1:
int main (int argc, argv) {
int x = 4;
int *y = &x;
int *z[4] = {NULL, NULL, NULL, NULL};
int a[4] = {1, 2, 3, 4};
Step 2:
z[0] = a;
z[1] = a + 1;
z[2] = a + 2;
z[3] = a + 3;
Step 3: No change in z’s values
z[0] = (int *)((char *)a);
z[1] = (int *)((char *)a
+ sizeof(int));
z[2] = (int *)((char *)a
+ 2 * sizeof(int));
z[3] = (int *)((char *)a
+ 3 * sizeof(int)); 0x3bc 0x3b8 0x3b4 0x3b0 4 3 2 1 NA 0x3d4 0x3d0 z[3] z[2] z[1] z[0] a[3] a[2] a[1] a[0] NA x y
Getting Fancy with Macros : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Getting Fancy with Macros #define QNODE(type) \
struct { \
struct type *next; \
struct type **prev; \
}
#define QNODE_INIT(node, field) \
do { \
(node)->field.next = (node); \
(node)->field.prev = \
&(node)->field.next; \
} while ( /* */ 0 );
#define QFIRST(head, field) \
((head)->field.next)
#define QNEXT(node, field) \
((node)->field.next)
#define QEMPTY(head, field) \
((head)->field.next == (head))
#define QFOREACH(head, var, field) \
for ((var) = (head)->field.next; \
(var) != (head); \
(var) = (var)->field.next) #define QINSERT_BEFORE(loc, node, field) \
do { \
*(loc)->field.prev = (node); \
(node)->field.prev = \
(loc)->field.prev; \
(loc)->field.prev = \
&((node)->field.next); \
(node)->field.next = (loc); \
} while (/* */0)
#define QINSERT_AFTER(loc, node, field) \
do { \
((loc)->field.next)->field.prev = \
&(node)->field.next; \
(node)->field.next = (loc)->field.next; \
(loc)->field.next = (node); \
(node)->field.prev = &(loc)->field.next; \
} while ( /* */ 0)
#define QREMOVE(node, field) \
do { \
*((node)->field.prev) = (node)->field.next; \
((node)->field.next)->field.prev = \
(node)->field.prev; \
(node)->field.next = (node); \
(node)->field.prev = &((node)->field.next); \
} while ( /* */ 0)
After Preprocessing and Compiling : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab typedef struct wth_t {
int state;
QNODE(wth_t) alist;
} wth_t; #define QNODE(type) \
struct { \
struct type *next; \
struct type **prev; \
} After Preprocessing and Compiling typedef struct wth_t {
int state;
struct {
struct wth_t *next;
struct wth_t **prev;
} alist;
} wth_t; state
next
prev 3 words in memory #define QNODE_INIT(node, field) \
do { \
(node)->field.next = (node); \
(node)->field.prev = &(node)->field.next;\
} while ( /* */ 0 );
QNODE Manipulations : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab #define QINSERT_BEFORE(head, node, alist)\
do { \
*(head)->alist.prev = (node); \
(node)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node)->alist.next;\
(node)->alist.next = (head); \
} while (/* */0) QNODE Manipulations QINSERT_BEFORE(head, node0, alist); ? before
QNODE Manipulations : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab #define QINSERT_BEFORE(head, node, alist)\
do { \
*(head)->alist.prev = (node); \
(node)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node)->alist.next;\
(node)->alist.next = (head); \
} while (/* */0) QINSERT_BEFORE(head, node0, alist); QNODE Manipulations before
QNODE Manipulations : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab #define QINSERT_BEFORE(head, node, alist)\
do { \
*(head)->alist.prev = (node); \
(node)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node)->alist.next;\
(node)->alist.next = (head); \
} while (/* */0) QINSERT_BEFORE(head, node0, alist); QNODE Manipulations before
QNODE Manipulations : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab #define QINSERT_BEFORE(head, node, alist)\
do { \
*(head)->alist.prev = (node); \
(node)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node)->alist.next;\
(node)->alist.next = (head); \
} while (/* */0) QINSERT_BEFORE(head, node0, alist); QNODE Manipulations before
QNODE Manipulations : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab #define QINSERT_BEFORE(head, node, alist)\
do { \
*(head)->alist.prev = (node); \
(node)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node)->alist.next;\
(node)->alist.next = (head); \
} while (/* */0) QINSERT_BEFORE(head, node0, alist); QNODE Manipulations before
QNODE Manipulations : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab #define QINSERT_BEFORE(head, node, alist)\
do { \
*(head)->alist.prev = (node); \
(node)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node)->alist.next;\
(node)->alist.next = (head); \
} while (/* */0) QINSERT_BEFORE(head, node0, alist); QNODE Manipulations before
Adding a Third Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Adding a Third Node QINSERT_BEFORE(head, node1, alist); #define QINSERT_BEFORE(head, node, alist)\
do { \
*(head)->alist.prev = (node); \
(node)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node)->alist.next; \
(node)->alist.next = (head); \
} while (/* */0)
Adding a Third Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Adding a Third Node QINSERT_BEFORE(head, node1, alist); #define QINSERT_BEFORE(head, node1, alist)\
do { \
*(head)->alist.prev = (node1); \
(node1)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node1)->alist.next; \
(node1)->alist.next = (head); \
} while (/* */0) (1) (1)
Adding a Third Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Adding a Third Node QINSERT_BEFORE(head, node1, alist); #define QINSERT_BEFORE(head, node1, alist)\
do { \
*(head)->alist.prev = (node1); \
(node1)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node1)->alist.next; \
(node1)->alist.next = (head); \
} while (/* */0) (1) (2) (2)
Adding a Third Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Adding a Third Node QINSERT_BEFORE(head, node1, alist); #define QINSERT_BEFORE(head, node1, alist)\
do { \
*(head)->alist.prev = (node1); \
(node1)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node1)->alist.next; \
(node1)->alist.next = (head); \
} while (/* */0) (3) (3)
Adding a Third Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Adding a Third Node QINSERT_BEFORE(head, node1, alist); #define QINSERT_BEFORE(head, node1, alist)\
do { \
*(head)->alist.prev = (node1); \
(node1)->alist.prev = (head)->alist.prev; \
(head)->alist.prev = &(node1)->alist.next; \
(node1)->alist.next = (head); \
} while (/* */0) (1) (1) (2) (2) (3) (3) (4) (4)
Removing a Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Removing a Node QREMOVE(node0, alist); #define QREMOVE(node, alist) \
do { \
(1) *((node)->alist.prev) = (node)->alist.next; \
(2) ((node)->alist.next)->alist.prev = (node)->alist.prev;\
(3) (node)->alist.next = (node); \
(4) (node)->alist.prev = &((node)->alist.next); \
} while ( /* */ 0)
Removing a Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Removing a Node QREMOVE(node0, alist); #define QREMOVE(node, alist) \
do { \
*((node)->alist.prev) = (node)->alist.next; \
((node)->alist.next)->alist.prev = (node)->alist.prev;\
(node)->alist.next = (node); \
(node)->alist.prev = &((node)->alist.next); \
} while ( /* */ 0)
Removing a Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Removing a Node QREMOVE(node0, alist); #define QREMOVE(node0, alist) \
do { \
(1) *((node0)->alist.prev) = (node0)->alist.next; \
((node0)->alist.next)->alist.prev = (node0)->alist.prev;\
(node0)->alist.next = (node0); \
(node0)->alist.prev = &((node0)->alist.next); \
} while ( /* */ 0) (1)
Removing a Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Removing a Node QREMOVE(node0, alist); #define QREMOVE(node0, alist) \
do { \
*((node0)->alist.prev) = (node0)->alist.next; \
(2) ((node0)->alist.next)->alist.prev = (node0)->alist.prev;\
(node0)->alist.next = (node0); \
(node0)->alist.prev = &((node0)->alist.next); \
} while ( /* */ 0) (2)
Removing a Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Removing a Node QREMOVE(node0, alist); #define QREMOVE(node0, alist) \
do { \
*((node0)->alist.prev) = (node0)->alist.next; \
((node0)->alist.next)->alist.prev = (node0)->alist.prev;\
(3) (node0)->alist.next = (node0); \
(node0)->alist.prev = &((node0)->alist.next); \
} while ( /* */ 0) (3)
Removing a Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Removing a Node QREMOVE(node0, alist); #define QREMOVE(node0, alist) \
do { \
*((node0)->alist.prev) = (node0)->alist.next; \
((node0)->alist.next)->alist.prev = (node0)->alist.prev;\
(node0)->alist.next = (node0); \
(4) (node0)->alist.prev = &((node0)->alist.next); \
} while ( /* */ 0) (4)
Solution to Removing a Node : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Solution to Removing a Node QREMOVE(node0, alist); #define QREMOVE(node, alist) \
do { \
(1) *((node)->alist.prev) = (node)->alist.next; \
(2) ((node)->alist.next)->alist.prev = (node)->alist.prev;\
(3) (node)->alist.next = (node); \
(4) (node)->alist.prev = &((node)->alist.next); \
} while ( /* */ 0)
Functions : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Functions Always use function prototypes int myfunc (char *, int, struct MyStruct *); int myfunc_noargs (void); void myfunc_noreturn (int i);
C and C++ are call by value, copy of parameter passed to function
C++ permits you to specify pass by reference
if you want to alter the parameter then pass a pointer to it (or use references in C++)
If performance is an issue then use inline functions, generally better and safer than using a macro. Common convention
define prototype and function in header or name.i file
static inline int myinfunc (int i, int j);
static inline int myinfunc (int i, int j) { ... }
Basic Types and Operators : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Basic Types and Operators Basic data types
Types: char, int, float and double
Qualifiers: short, long, unsigned, signed, const
Constant: 0x1234, 12, “Some string”
Enumeration:
Names in different enumerations must be distinct
enum WeekDay_t {Mon, Tue, Wed, Thur, Fri};enum WeekendDay_t {Sat = 0, Sun = 4};
Arithmetic: +, -, *, /, %
prefix ++i or --i ; increment/decrement before value is used
postfix i++, i--; increment/decrement after value is used
Relational and logical: <, >, <=, >=, ==, !=, &&, ||
Bitwise: &, |, ^ (xor), <<, >>, ~(ones complement)
Operator Precedence (from “C a Reference Manual”, 5th Edition) : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Operator Precedence (from “C a Reference Manual”, 5th Edition)
Structs and Unions : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Structs and Unions structures
struct MyPoint {int x, int y};
typedef struct MyPoint MyPoint_t;
MyPoint_t point, *ptr;
point.x = 0;point.y = 10;
ptr = &point; ptr->x = 12; ptr->y = 40;
unions
union MyUnion {int x; MyPoint_t pt; struct {int 3; char c[4]} S;};
union MyUnion x;
Can only use one of the elements. Memory will be allocated for the largest element
Conditional Statements (if/else) : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Conditional Statements (if/else) if (a < 10)
printf(“a is less than 10\n”);
else if (a == 10)
printf(“a is 10\n”);
else
printf(“a is greater than 10\n”);
If you have compound statements then use brackets (blocks)
if (a < 4 && b > 10) { c = a * b; b = 0; printf(“a = %d, a\’s address = 0x%08x\n”, a, (uint32_t)&a);} else { c = a + b; b = a;}
These two statements are equivalent:
if (a) x = 3; else if (b) x = 2; else x = 0;
if (a) x = 3; else {if (b) x = 2; else x = 0;}
Is this correct?
if (a) x = 3; else if (b) x = 2;else (z) x = 0; else x = -2;
Conditional Statements (switch) : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Conditional Statements (switch) int c = 10;
switch (c) {
case 0:
printf(“c is 0\n”);
break;
...
default:
printf(“Unknown value of c\n”);
break;
}
What if we leave the break statement out?
Do we need the final break statement on the default case?
Loops : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Loops flow control
break – exit innermost loop
continue – perform next iteration of loop
Note, all these forms permit one statement to be executed. By enclosing in brackets we create a block of statements. for (i = 0; i < MAXVALUE; i++) { dowork();}
while (c != 12) { dowork();}
do { dowork();} while (c < 12);
Building your program : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Building your program For all labs and programming assignments:
you must supply a make file
you must supply a README file that describes the assignment and results. This must be a text file, no MS word.
of course the source code and any other libraries or utility code you used
you may submit plots, they must be postscript or pdf
make and Makefiles, Overview : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab make and Makefiles, Overview Why use make?
convenience of only entering compile directives once
make is smart enough (with your help) to only compile and link modules that have changed or which depend on files that have changed
allows you to hide platform dependencies
promotes uniformity
simplifies my (and hopefully your) life when testing and verifying your code
A makefile contains a set of rules for building a programtarget ... : prerequisites ... command ...
Static pattern rules.
each target is matched against target-pattern to derive stem which is used to determine prereqs (see example)targets ... : target-pattern : prereq-patterns ... command ...
Makefiles : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Makefiles Defining variablesMyOPS := -DWTHMyDIR ?= /home/fredMyVar = $(SHELL)
Using variablesMyFLAGS := $(MyOPS)
Built-in Variables
$@ = filename of target
$< = name of the first prerequisites
Patterns
use % character to determine stem
foo.o matches the pattern %.o with foo as the stem.
foo.o moo.o : %.o : %.c # says that foo.o depends on foo.c and moo.o depends on moo.c
Example Makefile for wulib : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Example Makefile for wulib # Project specific
include ../Makefile.inc
INCLUDES = ${WUINCLUDES} –I.
LIBS = ${WILIBS} ${OSLIBS}
CFLAGS = ${WUCLFAGS} –DWUDEBUG
CC = ${WUCC}
HDRS := util.h
CSRCS := testapp1.c testapp2.c
SRCS := util.c callout.c
COBJS = $(addprefix ${OBJDIR}/, \
$(patsubst %.c,%.o,$(CSRCS)))
OBJS = $(addprefix ${OBJDIR}/, \
$(patsubst %.c,%.o,$(SRCS)))
CMDS = $(addprefix ${OBJDIR}/, $(basename $(CSRCS)))
all : $(OBJDIR) $(CMDS)
install : all
$(OBJDIR) :
mkdir $(OBJDIR)
$(OBJS) $(COBJS) : ${OBJDIR}/%.o : %.c $(HDRS)
${CC} ${CFLAGS} ${INCLUDES} –o $@ -c $<
$(CMDS) : ${OBJDIR}/% : ${OBJDIR}/%.o $(OBJS)
${CC} ${CFLAGS} -o $@ $@.o ${LIBS}
chmod 0755 $@
clean :
/bin/rm -f $(CMDS) $(OBJS) # Makefile.inc
# Contains common definitions
MyOS := $(shell uname -s)
MyID := $(shell whoami)
MyHost := $(shell hostname)
WARNSTRICT := -W \
-Wstrict-prototypes \
-Wmissing-prototypes
WARNLIGHT := -Wall
WARN := ${WARNLIGHT}
ALLFLGS := -D_GNU_SOURCE \
-D_REENTRANT \
-D_THREAD_SAFE
APPCFLGS = $(ALLFLGS) \
$(WARN)
WUCC := gcc
WUCFLAGS := -DMyOS=$(MyOS) \
$(OSFLAGS) \
$(ALLFLGS) $(WARN)
WUINCLUDES :=
WULIBS := -lm
ifeq (${MyOS), SunOS)
OSLIBS+= -lrt
endif Makefile.inc Makefile
Project Documentation : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Project Documentation README file structure
Section A: Introductiondescribe the project, paraphrase the requirements and state your understanding of the assignments value.
Section B: Design and ImplementationList all files turned in with a brief description for each. Explain your design and provide simple psuedo-code for your project. Provide a simple flow chart of you code and note any constraints, invariants, assumptions or sources for reused code or ideas.
Section C: ResultsFor each project you will be given a list of questions to answer, this is where you do it. If you are not satisfied with your results explain why here.
Section D: ConclusionsWhat did you learn, or not learn during this assignment. What would you do differently or what did you do well.
Attacking a Project : Fred Kuhns (6/10/2011) CSE332– Object Oriented Programming Lab Attacking a Project Requirements and scope: Identify specific requirements and or goals. Also note any design and/or implementation environment requirements.
knowing when you are done, or not done
estimating effort or areas which require more research
programming language, platform and other development environment issues
Approach: How do you plan to solve the problem identified in the first step. Develop a prototype design and document. Next figure out how you will verify that you did satisfy the requirements/goals. Designing the tests will help you to better understand the problem domain and your proposed solution
Iterative development: It is good practice to build your project in small pieces. Testing and learning as you go.
Final Touches: Put it all together and run the tests identified in the approach phase. Verify you met requirements. Polish you code and documentation.
Turn it in: