Coal presentationt
- 2. FLOPPY DISK 3 ½ INCH 5 ¼ INCH HARD DISK FILE ALLOCATION DISK STRUCTURES: Tracks, sectors, and cylinders. Disk partitions. Disk capacity. DISK STRUCTURES
- 4. FILE FILE HANDLING FILE HANDLE FILE ERRORS FILE POINTER OPERATIONS OF FILE • 3CH • 3DH • 3EH • 3FH • 40H • 41H • 42H FILE HANDLING
- 5. DISK STRUCTURES The actual physical details of disk
- 6. FLOPPY DISK
- 7. 1)Internal parts of a 3½-inch floppy disk. 2)A hole that indicates a high-capacity disk. 3)The hub that engages with the drive motor. 4)A shutter that protects the surface when removed from the drive. 5)The plastic housing. 6)A polyester sheet reducing friction against the disk media as it rotates within the housing. 7)The magnetic coated plastic disk. 8)A schematic representation of one sector of data on the disk; the tracks and sectors are not visible on actual disks. 9)The write protection tab (unlabeled) is upper left.
- 8. 3 ½ INCH 5 ¼ INCH
- 9. HARD DISK
- 10. 1) Actuator that moves the read-write arm. 2) Read-write arm swings read-write head back and forth across platter. 3) Central spindle allows platter to rotate at high speed. 4) Magnetic platter stores information in binary form. 5) Plug connections link hard drive to circuit board in personal computer. 6) Read-write head is a tiny magnet on the end of the read-write arm. 7) Circuit board on underside controls the flow of data to and from the platter. 8) Flexible connector carries data from circuit board to read-write head and platter. 9) Small spindle allows read- write arm to swing across platter.
- 11. WORKING OF HARD DISK
- 14. CAPACITY OF THE 5 ¼ INCH DOUBLE DENSITY FLOPPY DISK
- 15. CAPACITY OF HARD DISK
- 16. FILE ALLOCATION To keep the track of data stored on a disk, DOS uses a directory structure. The first tracks and sectors of a disk contain information about the disk’s file structure.
- 18. FILE DIRECTORY:
- 19. ATTRIBUTE BYTE
- 20. Cluster “A fixed number of sector (depends on the kind of disk) is called cluster”
- 21. (File Allocation Table): “A table that the operating system uses to locate files on a disk. Due to fragmentation, a file may be divided into many sections that are scattered around the disk. The FAT keeps track of all these pieces.” F A T
- 22. DOS HOW DOS READ A FILE? • DOS gets the starting cluster number from directory. • DOS read that particular cluster number from disk and stored in DTA (Data Transfer Area). The program that initiated the read retrieves data from HOW DOS STORES A FILE? • DOS locates an unused directory entry and stores the filename, attribute, creation time and date. • DOS searches the FAT for the first entry indicating unused cluster (000 means unused) and stores the starting cluster number in the directory. Let’s suppose
- 23. FILE HANDLING
- 24. FILE FILE HANDLING FILE HANDLE FILE ERRORS FILE POINTER OPERATIONS OF FILE • 3CH • 3DH • 3EH • 3FH • 40H • 41H • 42H FILE HANDLING
- 25. File ? File Handling ? A file is an object on a computer that stores data, information, settings, or commands that are used with a computer program. Through file handling, one can perform operations like create, modify , delete etc on File. File Create Write Rename Delete
- 26. FILE HANDLES When file is created or open in a program, DOS assign it a unique number called file handle.
- 28. FILE ERRORS
- 32. 3CH 42H 3EH3DH 40H 41H3FH OPEN A NEW FILE / REWRITE A NEW FILE MOVE A FILE POINTER DELETE A FILEWRITE A FILEREAD A FILE CLOSE A FILE OPEN AN EXISTING A FILE
- 33. Creating File & Writing FILE DB "c:example_newhello.txt",0 TEXT DB "HELLO I AM TEXT",0 TEXT_SIZE = $ - OFFSET TEXT HANDLE DW ? System Call AH BX CX DX File Open 3CH 0 Offset Filename File Write 40H Handle Text Size Offset Text File Close 3EH Handle Handle ? Handle is some resources/memory to store temporary data , used in file operation
- 34. Create File Operation MOV CX,0 MOV DX, OFFSET FILE ; FILENAME MOV AH, 3CH ; 3CH FOR CREATING FILE INT 21H Write into File MOV HANDLE, AX ; MAKE RESOURCES HANDLE MOV AH, 40H ; 40H FOR WRITING INTO FILE MOV BX, HANDLE ; COPY RESOURCES HANDLE MOV DX, OFFSET TEXT ; TEXT TO WRITE MOV CX, TEXT_SIZE ; TEXT SIZE INT 21H;
- 35. Close File MOV AH, 3EH ; 3EH FOR CLOSE FILE MOV BX, HANDLE ; COPY RESOURCES HANDLE INT 21H
- 36. Delete File .DATA FILE DB "C:EXAMPLE_NEWWORLD.TXT",0 .CODE MOV DX, OFFSET FILE ; OLD FILENAME MOV AH, 41H ; 41H FOR DELETE FILE INT 21H System Call AH BX CX DX File Delete 41H Offset OldFilename
- 37. File pointer The file pointer is used to locate a position in the file. File is opened – file pointer is at the beginning of file. After read operation – it the next byte to be read. After writing – file pointer at end of file.
- 38. File pointer Move File pointer INT 21H, FUNCTION 42H INPUT AH = 42H AL = MOVEMENT CODE: • 0 MOVE RELATIVE TO BEGINNIG • 1 MOVE RELATIVE TO CUUERENT POINTER LOCATION • 2 MOVE RELATIVE TO THE EOF BX = FILE HANDLE CX:DX = NUMBER OF BYTES TO MOVE OUTPUT DX:AX = NEW POINTER LOCATION IN BYTES FROM THE BEGNNING OF FILE. IF CF = 1 ERROR CODE IN AX (1,6). System Call AH BX CX:DX File pointer 42H File handle Number of byte to move
- 39. Caption