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File io File io Presentation Transcript

  • C Programming Language By: Yogendra Pal yogendra@learnbywatch.com Dedicated to My mother and Father
  • t y Keep your notebook with you. Write important point and questions that comes in your mind Solve Mind band exercise. C Rewind when not clear Ask Questions by call or SMS or by mail Keep Watching Keep Learning THIS IS FILE I/O 2
  • File… • Files are used to store data to disks. • Data on disk is permanent. • Variables are stored on RAM only. • Data on RAM can not be accessed later. 3
  • File… • File : Group of related records. Sonu 001 04/02 Amit 002 09/05 File Asif 003 10/09 Hari 004 30/11 Sonu 001 04/02 Record Sonu Field 1001001 byte 1 bit 4
  • Files in C • A file is a sequence of bytes. – File ends with End Of File (EOF) marker. • Streams are used to communicate with file. stream 5
  • File • Use FILE pointer to access a file. FILE *fp; • fopen() library function is used to open a file. – fopen( file_path, open_mode); – Returns NULL if file can not open. • fclose() library function is used to close a file. – fclose(file_pointer); 6
  • File open mode Mode Description r Open a file for reading. w Create a file for writing. If the file already exists, discard the current contents. a Append; open or create a file for writing at end of file. r+ Open a file for update (reading and writing). w+ Create a file for update. If the file already exists, discard the current contents. a+ Append; open or create a file for update; writing is done at the end of the file. rb Open a file for reading in binary mode. wb Create a file for writing in binary mode. If the file already exists, discard the current contents. ab Append; open or create a file for writing at end of file in binary mode. rb+ Open a file for update (reading and writing) in binary mode. wb+ Create a file for update in binary mode. If the file already exists, discard the current contents. ab+ Append; open or create a file for update in binary mode; writing is done at the end of the file. 7
  • Read / Write a file • fgetc() : reads one character from a file. • fputc() : write one character to a file. • fgets() : read a line (Srring) from a file. • fputs() : Write a line to a file. • fprintf() : used to print to a file. • fscanf() : used to read from a file. • feof() : return true if EOF find. • rewind() : set file position pointer to the start. 8
  • Problem • Write a program to read a file and print it on monitor. • Write a program to create a copy of a file. • Modify first problem: stop printing if a ‘z’ occurs in file. • Write a program to create a file. 9
  • Sequential Access File • Write or Read data sequentially. • Data can not modify without destroying. • Fields can vary in size. fopen(“one.dat”, “w”); 10
  • Random Access File • Access any record without searching through other records. • Data can be inserted without destroying other data. • Implemented using fixed length records. fopen(“one.dat”, “wb”); • Also known as binary file. 11
  • Random Access File… • fwrite() : used to write to binary file. • fread() : read from binary file. • fseek(): Used to set the file position pointer to a specific location. • Operation sequention. – Open/Create->seek->Write. – Open->seek->Read. 12
  • fwrite() / fread() • fwrite(&data,sizeof(data),1,fp); • data : data that you want to write to file. • sizeof(data) : number of bytes to write. • 1 : for arrays, number of elements to write. • fp : file to write. – fread(&data,sizeof(data),1,fp); • &data : variable to store data. • sizeof(data) : number of bytes to read. • 1 : for arrays, number of elements to read. • fp : file from read. 13
  • fseek() • fseek(fp,offset,symbolic_constant); – fp : File pointer. – offset : location of file position pointer. – symbolic_constant : specify where in file we are reading from. • SEEK_SET: beginning of file. • SEEK_CUR: current location in file. • SEEK_END: end of file. 14
  • To get complete benefit of this tutorial solve all the quiz on www.learnbywatch.com For any problem in this tutorial mail me at yogendra@learnbywatch.com with the subject “C” For Other information mail at info@learnbywatch.com Keep Watching Keep Learning NOW YOU ARE READY TO LEARN C++ AND JAVA