1. Programming Fundamental
Instructor Name: Muhammad Safyan
Lecture-18

2. Lecture outline
String handling
Character handling

3. String Handling

4. String Handling Initializing String string month = "March";
string text( "Hello" );
#include<iostream>
#include<conio.h>
using namespace std;
main ( ) {
string month = "March";
string text( "Hello" );
cout<< month<<endl;
cout<<text;
getch(); }

5. String Assignment string string1( "cat" ); string string2;
string2 = string1; // assign string1 to string2
string3.assign( string1 ); // assign string1 to string3
string2[ 0 ] = string3[ 2 ] = 'r';
#include<iostream>
#include<conio.h>
using namespace std;
main ( ) {
string string1( "cat" );
string string2;
string string3;
string2 = string1; // assign string1 to string2
cout<<string2;
string3.assign( string1 ); // assign string1 to string3
string2[ 0 ] = string3[ 2 ] = 'r';
cout<<string3;
getch(); }

6. String Concatenation // demonstrating member function at
for ( int i = 0; i < string3.length(); i++ )
cout << string3.at( i );
string a("gc university lahore");
string b=a+" Pakistan";
b.append(" Asia");
string string5;
string5.append( a, 4, a.length() - 4 );
string a("gc university lahore");
for(int i=0; i<a.length(); i++)
cout<<a.at(i);

7. Substrings string a("gc university lahore");
cout<<a.substr(2,7);

8. Swapping strings string a("gc university lahore");
string b("paksitan");
a.swap(b);
cout<<a<<endl;
cout<<b;

9. Erase ,Find and Insert string a="department of computer science";
cout<<a.erase(2);
cout<<a.erase(2,5);
int position = a.find(" ");
cout<<position;
string1.insert( 10, string2 );
#include<iostream>
#include<conio.h>
using namespace std;
main ( ) {
string a="safyan";
string string1="department of computer science";
string1.insert( 10, a);
cout<<endl<<string1;
getch(); }

10. #include<ctype.h>
Header File
ctype.h
#include<ctype.h>
Storage Requirements for Text and Binary Modes
Storage Requirements for Text and Binary Modes
for an Integer:
for an Integer:
Page 32
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The fwrite() Function
The fwrite() Function
size_t fwrite (void *ptr, size_t size, size_t nmemb,
size_t fwrite (void *ptr, size_t size, size_t nmemb,
FILE *fp);
FILE *fp);
fwrite() writes, from the address pointed to by ptr,
fwrite() writes, from the address pointed to by ptr,
up to nmemb elements whose size is specified by
up to nmemb elements whose size is specified by
size, to the file pointed by fp
size, to the file pointed by fp
fwrite() returns the number of elements
fwrite() returns the number of elements
successfully written, which will be less than nmemb
successfully written, which will be less than nmemb
only if a write error is encountered.
only if a write error is encountered.
double earnings[10];
double earnings[10];
fwrite(earnings,sizeof(double),10,fp);
fwrite(earnings,sizeof(double),10,fp); 32 32
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The fread() Function
The fread() Function
size_t fread(void *ptr, size_t size, size_t nmemb,
size_t fread(void *ptr, size_t size, size_t nmemb,
FILE *fp);
FILE *fp);
fread() reads, into the array pointed to by ptr, up to
fread() reads, into the array pointed to by ptr, up to
nmemb elements whose size is specified by size,
nmemb elements whose size is specified by size,
form the file pointed to by fp.
form the file pointed to by fp.
fread() returns the number of elements
fread() returns the number of elements
successfully read, which may be less than nmemb
successfully read, which may be less than nmemb
is a read error or end-of-file is encountered.
is a read error or end-of-file is encountered. 33 33
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Writing file data using block I/O functions
Writing file data using block I/O functions
#include <stdio.h>
#include <stdio.h>
typedef struct {
typedef struct {
char name[20];
char name[20];
int serial_code;
int serial_code;
int amount;
int amount;
float
float
cost;
cost;
} component;
} component;
main(void)
main(void)
{ component comp_data;
{ component comp_data;
FILE
FILE
*fp;
*fp;
char
char
filename[80];
filename[80];
int numofcomp;
int numofcomp;
int i;
int i;
printf("Enter the file name: ");
printf("Enter the file name: ");
gets(filename);
gets(filename); 34 34
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if ((fp = fopen(filename, "wb")) == NULL) {
if ((fp = fopen(filename, "wb")) == NULL) {
printf("can't open file \n");
printf("can't open file \n");
exit(1);
exit(1);
}printf("Enter the number of components: ");
}printf("Enter the number of components: ");
scanf("%d", &numofcomp);
scanf("%d", &numofcomp);
for (i=0; i<numofcomp; i++) {
for (i=0; i<numofcomp; i++) {
printf("Name of the component: ");
printf("Name of the component: ");
gets(comp_data.name);
gets(comp_data.name);
printf("Serial code of the component: ");
printf("Serial code of the component: ");
scanf("%d", &comp_data.serial_code);
scanf("%d", &comp_data.serial_code);
printf("Amount of the component: ");
printf("Amount of the component: ");
scanf("%d", &comp_data.amount);
scanf("%d", &comp_data.amount);
printf("Cost of each component: ");
printf("Cost of each component: ");
scanf("%f", &comp_data.cost);
scanf("%f", &comp_data.cost);
fwrite(&comp_data, sizeof(comp_data), 1, fp);
fwrite(&comp_data, sizeof(comp_data), 1, fp);
}fclose(fp);
}fclose(fp);
return 0;
return 0; } } 35 35
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12.5 Random Access
12.5 Random Access
Random Access: fseek() and ftell()
Random Access: fseek() and ftell()
fseek, ftell: All the previous I/O functions do reading
fseek, ftell: All the previous I/O functions do reading
and writing sequentially, i.e. read the 1st datum, 2rd
and writing sequentially, i.e. read the 1st datum, 2rd
datum, 3rd datum ..., etc.
datum, 3rd datum ..., etc.
fseek
fseek
and
and
ftell
ftell
help doing
help doing
I/O in non-sequential manner, i.e. read the 10th
I/O in non-sequential manner, i.e. read the 10th
datum, then go back and read the 2nd datum.
datum, then go back and read the 2nd datum. 36 36
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File position pointer
File position pointer
The system keeps a file position pointer for
The system keeps a file position pointer for
each open file.
each open file.
It indicates the location in the file at
It indicates the location in the file at
which data will be read or written.
which data will be read or written.
file position marker
file position marker
......
......
Disk
Disk 37 37
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The fseek() Function
The fseek() Function
The function prototype of
The function prototype of
fseek()
fseek() is is
int fseek(FILE *fp, long int offset, int mode);
int fseek(FILE *fp, long int offset, int mode); * *
fseek()
fseek()
returns
returns
if OK, and
if OK, and -1 -1
if there is an error.
if there is an error. * *
offset
offset
tells how far to move from the starting point
tells how far to move from the starting point
(depending on the mode). It can be +ve (move
(depending on the mode). It can be +ve (move
forward) or -ve (move backward) or 0.
forward) or -ve (move backward) or 0. * *
mode
mode
identifies the starting point. In stdio.h, the
identifies the starting point. In stdio.h, the
following constants can be assigned to mode:
following constants can be assigned to mode:
Mode
Mode
Measure offset from
Measure offset from
SEEK_SET
SEEK_SET
Beginning of file
Beginning of file
SEEK_CUR
SEEK_CUR
Current position
Current position
SEEK_END
SEEK_END
End of file
End of file 38 38
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The ftell() Function
The ftell() Function
The function prototype of
The function prototype of
ftell()
ftell() is is
long int ftell(FILE *fp);
long int ftell(FILE *fp);
returns the current file location.
returns the current file location.
The rewind() Function
The rewind() Function
The function prototype of
The function prototype of
rewind()
rewind() is is
void rewind(FILE *fp);
void rewind(FILE *fp);
Resets the file position marker to the beginning of
Resets the file position marker to the beginning of
the file. This is equivalent to
the file. This is equivalent to
fseek(fp, 0L, SEEK_SET);
fseek(fp, 0L, SEEK_SET); 39 39
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/* reverse.c - displays a file in reverse order */
/* reverse.c - displays a file in reverse order */
#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdlib.h>
#define CNTL_Z '\032'
#define CNTL_Z '\032'
/* eof marker in DOS textfiles */
/* eof marker in DOS textfiles */
{ int main(int argc, char *argv[])
{ int main(int argc, char *argv[])
char ch;
char ch;
FILE *fp;
FILE *fp;
long count, last;
long count, last;
if ((fp=fopen(argv[1],"rb"))== NULL) {
if ((fp=fopen(argv[1],"rb"))== NULL) {
printf("reverse can't open %s\n", argv[1]);
printf("reverse can't open %s\n", argv[1]);
exit(1);
exit(1); } }
fseek(fp,0L, SEEK_END);
fseek(fp,0L, SEEK_END);
/* goto eof */
/* goto eof */
last=ftell(fp);
last=ftell(fp);
for (count=1L; count<=last; count++) {
for (count=1L; count<=last; count++) {
fseek(fp,-count,SEEK_END);
fseek(fp,-count,SEEK_END);
ch=getc(fp);
ch=getc(fp);
if (ch!=CNTL_Z && ch!= '\r')
if (ch!=CNTL_Z && ch!= '\r')
putchar(ch);
putchar(ch);
}fclose(fp);
}fclose(fp);
return(0);
return(0); 40 40 } }

11. Example #include<iostream> #include<conio.h>
using namespace std;
main ( ) {
int i ;
char c ;
for( i = 0; i < 256 ; i ++ )
c = i ;
cout<<i <<"\t" << c <<endl ; }
getch();

12. ctype Functions int isspace ( int c ) int isdigit ( int c )
int isalpha ( int c )
int isalnum ( int c )
int isxdigit ( int c )
int islower ( int c )
int isupper ( int c )
int tolower ( int c )
int toupper ( int c )

13. isdigit ( ) Function
int isdigit ( int c ) ;

14. isalpha ( ) Function
int isalpha ( int c ) ;

15. isalnum ( ) Function
int isalnum ( int c ) ;

16. islower ( ) Function
int islower ( int c ) ;

17. isupper ( ) Function
int isupper ( int c ) ;

18. tolower ( ) Function
int tolower ( int c ) ;

19. toupper ( ) Function
int toupper ( int c ) ;

20. getchar ( ) ;

21. #include<string>
#include<conio.h>
#include<iostream.h>
using namespace std;
//#include<ctype.h>
main() {
int lc=0; int uc=0; int dig=0; int ws=0; int pun=0; int oth=0;
char c;
cout<<"enter characters";
while((c=getchar())!='\n')
if (islower(c))
lc ++ ;
else if (isupper(c))
uc ++ ;
else if (isdigit(c))
dig ++;
else if (isspace(c))
ws ++ ;
else if (ispunct(c))
pun ++ ;
else
oth ++ ; }
cout<<"lower character"<<lc;
getch();