Sequential & Random File Creation

1. Sequential & Random File Creation SRM-MCA

2. // Program uses fgets() to get a String from the File #include<stdio.h> #include<conio.h> void main() { FILE *fp; char s[80],n[25]; int c; clrscr(); printf("\n Enter Your Filename :"); gets(n); fp=fopen(n,"r"); if(fp==NULL) { printf("\n Cannot open a File"); exit(0); } c=0; printf("\n The Contents of your file is\n"); while(fgets(s,80,fp)!=NULL) { printf("%s",s); c++; } printf("Total Lines :%d\n\n",c); fclose(fp); getch(); } // Program uses fputs() to send a String to a File #include<stdio.h> #include<conio.h> void main() { FILE *fp; char s[80]; clrscr(); fp=fopen("t1.txt","w"); if(fp==NULL) { printf("\n Cannot open a File"); exit(1); } printf("\n Enter Your Text\n"); while(strcmp(gets(s),"end")!=0) { fputs(s,fp); } puts("Data Can Be Updated Sucessfully"); getch(); }

3. // Program uses fgetc() to get a character from the File #include<stdio.h> void main() { FILE *fp; char s[80]; int i,ch; fp=fopen("first.dat","r"); if(fp==NULL) { printf("\n Unable to open the File"); exit(0); } ch=fgetc(fp); for(i=0;i<80 && ch!=EOF;i++) { s[i]=ch; ch=fgetc(fp); } s[i]='\0'; printf("\n %s",s); fclose(fp); } // Program uses fputc() to send a character to an ASCII File #include<stdio.h> #include<conio.h> void main() { FILE *fptr; char strptr[]="This Is a Test \0"; char *p; clrscr(); fptr=fopen("first.dat","w"); if(fptr==NULL) { printf("\n Unable to open the File"); exit(); } for(p=strptr; *p != '\0';p++) { fputc(*p,fptr); } getch(); }

4. // file creation : writing data to a file #include<stdio.h> #include<conio.h> FILE *fp; void main() { char name[20]; int no; int sal; fp=fopen("emp.dat","w"); if(fp != NULL) { printf("\nEnter the number:"); scanf("%d",&no); printf("\nEnter the name:"); scanf("%s",&name); printf("\nEnter the salary:"); scanf("%d",&sal); fprintf(fp,"The no is %d\n",no); fprintf(fp,"The name is %s\n",name); fprintf(fp,"The salary is %d\n",sal); printf("\n Suceesfully Created"); } else { printf("\n File Cannot Opened"); exit(0); } fclose(fp); } Read the contents from the file #include<stdio.h> #include<conio.h> FILE *fp; void main() { char c; clrscr(); if((fp=fopen("emp.dat","r"))!=NULL) { while((c=getc(fp))!=EOF) putc(c,stdout); } else { printf("Error in opening a file"); } fclose(fp); getch(); }

5. Append the Data to an Existing File #include<stdio.h> FILE *fp; void main() { char name[20]; long int no; long int sal; if((fp=fopen (“emp.dat","a"))!=NULL) { printf("\n enter the number:"); scanf("%d",&no); printf("\n enter the name:"); scanf("%s",name); printf("\n enter the salary:"); scanf("%d",&sal); fprintf(fp,"the no is %d\n", no); fprintf(fp, "the name is %s\n",name); fprintf(fp, "the salary is %d\n",sal); } fclose (fp); }

6. RANDOM FILE CREATION Write a “C” Program to add, View ,Modify and Delete Records in Electricity Board Bill Preparation using Random File printf("\n 1. Add Record "); printf("\n 2.View Record"); printf("\n 3.Delete a Record"); printf("\n 4.Modify a record"); printf("\n 5.Terminate the Program"); CHOICE : printf("\n Enter your choice "); scanf("%d",&ch); if((ch<1) && (ch>5)) { goto CHOICE; } switch(ch) { case 1:add_record(); break; case 2:view_record(); break; case 3:del_record(); break; case 4:modify_record(); break; case 5:exit(0); } #include<stdio.h> #include<stdlib.h> #include<conio.h> #include<dos.h> void add_record(); void view_record(); void modify_record(); void del_record(); struct electric { long int scno; char pname[30]; char area[20]; float cur_reading; float pre_reading; }; void main() { int ch,i; MENU: clrscr(); goto MENU; } void add_record() { struct electric r; FILE *eb; char flag; eb=fopen("eb.dat","ab+"); clrscr(); do { printf("\n Enter Details"); scanf("%ld %s %s %f %f",&r.scno,r.pname,r.area,&r.pre_reading,&r.cur_reading); fwrite(&r,sizeof(r),1,eb); fflush(stdin); printf("\n Add another record [y/n];"); flag=getchar(); }while(toupper(flag)=='Y'); fclose(eb); }

7. void view_record() { struct electric r; FILE *eb; char flag; eb=fopen("eb.dat","rb+"); clrscr(); while((fread(&r,sizeof(r),1,eb)!=NULL)) { printf("\n The File datas Are \n\n"); printf("%ld %s %s %f %f",r.scno,r.pname,r.area,r.pre_reading,r.cur_reading); } } void del_record() { struct electric r; FILE *eb,*temp; long int no; char ch; temp=fopen("temp.dat","wb+"); eb=fopen("eb.dat","rb+"); clrscr(); printf("\n Enter the Number to Delete :"); scanf("%ld",&no); while((fread(&r,sizeof(r),1,eb)!=NULL)) { if(r.scno==no) { clrscr(); printf("\n The File datas Are \n\n"); printf("%ld %s %s %f %f",r.scno,r.pname,r.area,r.pre_reading,r.cur_reading); fflush(stdin); printf("\n Are U Sure to Delete this record[Y/N]:"); ch=getchar(); if(toupper(ch)=='Y') { fwrite(&r,sizeof(r),1,temp); continue; } } else { fwrite(&r,sizeof(r),1,temp); } } remove("eb.dat"); rename("temp.dat","eb.dat"); remove("temp.dat"); fclose(eb); fclose(temp); return; }

8. void modify_record() { struct electric r; FILE *eb; long int no,pos; char ch; eb=fopen("eb.dat","rb+"); clrscr(); printf("\n Enter the Service Number to modify :"); scanf("%ld",&no); while(eb!=NULL) { pos=ftell(eb); fread(&r,sizeof(r),1,eb); if(r.scno==no) { clrscr(); printf("\n The File datas Are \n\n"); printf("%ld %s %s %f %f",r.scno,r.pname,r.area,r.pre_reading,r.cur_reading); fflush(stdin); printf("\n Are U Sure to Modify this record[Y/N]:"); ch=getchar(); if(toupper(ch)=='Y') { printf("\n Enter Details"); scanf("%ld %s %s %f %f",&r.scno,r.pname, r.area,&r.pre_reading,&r.cur_reading); fseek(eb,0,pos); fwrite(&r,sizeof(r),1,eb); puts("Record Updated Sucessfully"); getch(); } } else { puts("Service Number Not Found"); } fclose(eb); return; } }

9. Points to be Remember • fopen() opens a stream for use and links a file with that stream • fclose() closes a stream that was opened by a call to fopen() • fputc()is used to write characters,fgetc() is used to read characters from an open file • fputs is used to write group of characters(string) fgets() is used to read group of characters from an open file • feof() is used to indicate end-of-file when the file is opened for binary operations • rewind() function resets the file position indicator to the beginning of the file • fprintf() is used to write any type of informations (any datatype) to an file,fscanf() is used to read any type of informations from an open file. • The ftell() used to indicate the current position of file pointer • The fseek() is used to set the position of filepointer which we can desired

10. Preprocessor Directives • Preprocessor directives are instructions given to the compiler. • They begin with a # sign and can be placed anywhere in the program but usually they are placed in the beginning of a program. • Some of the preprocessor directives # if # elif # ifdef #include # indef # define # else # undef

11. # define • The # define directive contains two parts : an identifier and a string that is to be substituted for the identifier, each time the identifier is encountered in the source file. # define identifier string • The identifier and string are separated by a space. • The identifier can be referred to as the macro name and the • string as the macro substitution.

12. # if ... # endif # if ... # else ... # endif # if ... # elif ... # endif Conditional Compilation Directives # if, # else, # elif, # endif Syntax :

13. printf("hai"); N; printf("%d",mul(2,3)); N; printf("%d",mysqrt(4)); N; printf("%s | %s | Line Number : %d",__FILE__,__DATE__,__LINE__); NF; NNN; } Example for Compiler Directives #define N putchar('\n') #define mul(x,y) ((x)*(y)) #define mysqrt(x) ((x) * (x)) #ifdef N #define FORMAT N,N #endif #ifdef FORMAT #undef FORMAT #define NF N,printf("hai"),N #endif #ifdef NF #ifndef FORMAT #define NNN N,printf("new"),N #endif #endif #include <stdio.h> void main() { Output hai 6 16 Compi~1.c | Feb 16 2008 | Line Number : 29 hai new

14. The const Keyword • It can be used to achieve almost the same effect as #define when creating constants. • Variables of type const can be given an initial value, but cannot be changed through the program. • Example : const int var = 35;

15. Session Summary • Storage of information to be read from or written on a auxillary memory device is stored in the form of file. • The data structure of a file is defined in stdio.h which creates a buffer area to store data in a file for reading as well as writing • Function fscanf() & fprintf() are used to perform I/O operations in file • Function fgetc() & fputc() are used to perform Character I/O operations in file • Function fgets() & fputs() are used to perform String I/O operations in file • Function fseek() used to index a file and can be used to increment or decrement the file pointer by any number of position in a file.

16. EXERCISES Write a program to reverse the contents of a text file? Write a program to count the number of characters in a text file? Write a program to count the number of words in a file? Write a program to merge three text files one by one? Explain the use of fseek() function in files? Explain the concept of I/O in files with the help of fscanf() and fprintf() functions?