These include a 10 key (0-9) numeric keypad and the cursor control keys. Also, beginning on the top row at the right, you see the NUM(eric) LOCK key, SCROLL LOCK key, PAUSE key, and the PRT SC (print screen) key.  Located  on  the  bottom  right-hand  side  of  the keyboard  are  the  INS(ert)  and  DEL(ete)  keys.  The purpose/function of each of these keys is as follows: FUNCTION  KEYS  F1-F12  These   special- purpose  keys  are  used  to  communicate  special functions to the operating system, such as MS- DOS, or to applications software. The meaning of  each  is  defined  by  the  particular  software. This   simplifies   tasks   that   might   otherwise require several keystrokes. These keys can also be used with other keys to increase the number of functions you can specify to a program. NUMERIC  KEYPAD  KEYS  To  activate  the numeric  keypad,  press  the  NUM  LOCK  key. The NUM LOCK key may contain an indicator light within the key to indicate when it is  ON. Use  the  numeric  keypad  just  like  a  calculator keypad  to  enter  numbers  you  will  be  using  in mathematical functions. CURSOR  CONTROL  KEYS  The   CURSOR CONTROL  keys  are  most  important.  They allow you to move the cursor from one place to another  on  the  display  screen.  Remember,  the cursor is the indicator, the spot of light on the screen, which lets the user know where the next entry will be made. On the keyboard shown in figure 1-17, the cursor control keys are located in two locations, both on the numeric keypad and as a separate keypad. When the NUM LOCK key is OFF, you can use the arrows on keys 2,4,6, and 8  to  control  cursor  movement  one  line  up  or down,  or  one  position  to  the  left  or  right,  as shown   by   the   direction   of   the   arrow.   The remaining cursor control keys on keys 1, 3, 7, and 9 are used to move the cursor to other parts of the  screen  or  document/data  (for  example,  the end of a line [END key] or the top of the next page [PgDn key]). Some software packages use the cursor control keys in combination with each other or with other keys to increase the number of ways and the speed with which you can move the cursor.  Read  the  software  documentation;  the faster and more efficiently you are able to move the cursor through a document or database, the faster and more efficiently you will get the job done.  Some  keyboards  have  separate  arrow  keys for  cursor  control.  This  is  particularly  helpful when   you   are   doing   a   lot   of   data   entry   of numbers. SCROLL LOCK KEY  Applications  software uses  the  SCROLL  LOCK  mode  of  the  key  to control screen scrolling. PAUSE   KEY   The  PAUSE  key  is  used  to interrupt program execution. PRT  SCreen  KEY  The  PRT  SCREEN  key  is activated by depressing it in conjunction with the SHIFT  key  depressed.  This  sends  whatever  is displayed  on  the  monitor’s  screen  to  the  printer. INSert  and  DELete  KEYS  These  keys  allow you to insert or delete a character at the position of  the  cursor  when  neither  the  SHIFT  nor  the NUM LOCK keys are depressed. It   is   important   to   remember   that   any   key   or combination of keys can be assigned special meaning by a program. Therefore, the keys may have different meanings and functions, depending on the program you are  using.  Once  again,  we  remind  you,  read  all  the documentation that comes with each program and with the computer system. Disks and Disk Drives Magnetic disks, regardless of their type or size, are, without a doubt, the most important secondary storage medium used with microcomputers. Disks provide fast retrieval   of   information. The   disk’s   physical characteristics,  flat  and  round,  allow  the  disk  drive direct access  to data. Put simply, the processing unit goes directly to a designated disk drive, seeks out the specific location on the disk where the data is stored, and immediately retrieves it. The disk drive does NOT have to read through a series of records before reaching the one desired, as is the case with magnetic tape units. The  two  forms  of  magnetic  disk  typically  used  with microcomputers are the floppy disk (diskette) and the hard disk.  Let’s look at the sizes and construction of each and at the disk drive devices that read from and write  to  them. DISKETTES   AND   THEIR   DRIVES.—   A diskette is also referred to as a floppy disk, or just plain floppy, because it is a round, flexible platter. Physical   Characteristics.—  The   platter   is enclosed in a plastic jacket. At present, diskettes come in two sizes (diameters): 5 1/4 (5.25) inches and 3 1/2 1-18