SECTION C                                             FILE INTRO.C
                               MODES OF OPERATION
                               ******************

              The BASIC system employs two distinct ways of working called 
          DIRECT MODE  and PROGRAM MODE . In DIRECT MODE commands are typed in 
          from the keyboard and are processed when RETURN is pressed. In 
          PROGRAM MODE the commands are taken from the program in memory and 
          are executed in program sequence.    
              DIRECT MODE may be subdivided into DIRECT COMMAND MODE, PROGRAM 
          INPUT MODE  and EDIT MODE.
           
          DIRECT COMMAND .     Only one line is  entered and does   
          ===================  not commence with a number. The line is typed 
          in at the cursor and is executed by pressing RETURN. Up to 255 
          characters can be written in one line including all punctuation 
          marks, symbols and spaces (A full 'line' in fact takes up about two 
          and a half actual lines of text) Several separate commands can be 
          put on one line separated by a colon, but on pressing RETURN the 
          line will be executed and then forgotten. To execute the same 
          command(s) again you would need to type the line afresh. The DIRECT 
          COMMAND is more usually used for short command lines, maybe just one 
          word. For example if a program was loaded, by typing RUN at the Ok 
          prompt and then pressing RETURN the program would execute or 'run' .    
          Other common single word commands are PRINT, LIST, LOAD and SAVE. 

          PROGRAM INPUT       This is the mode used to write programs. To
          =============       enter program input mode from direct command 
          mode simply type a valid line number at the prompt. As soon as this 
          first line number is typed you will be in program input mode. When 
          you press [RETURN] at the end of the line, the line will not execute 
          but simply be recorded in memory, and BASIC will wait for the next 
          line. Alternatively if a program is loaded, using the command LIST 
          at the cursor and pressing return will display the program in 
          program input mode. You will have seen this when trying the short 
          program earlier.

          EDIT MODE   When typing in a command line, whether in PROGRAM INPUT 
          =========   or DIRECT COMMAND mode the line can be altered or 
          'edited' until the RETURN key is pressed . This state is the EDIT 
          MODE and can be recognised by the cursor on the line. Characters can 
          be deleted or added at the cursor position until you are satisfied 
          with the EDIT. When a program is in memory any line can be called up 
          for editing by typing EDIT 100, where 100 is the line you want to 
          edit.When complete press RETURN to set. At other times, such as when 
          a syntax error is discovered by BASIC, the offending line will be 
          presented for your attention in EDIT MODE, complete with  cursor. 
          Another way of entering EDIT MODE which can be extremely useful 
          sometimes is by use of the AUTO command. but more of this later 
                
          PROGRAM MODE   When a program is loaded and you type RUN at the                
          ============   cursor ( in DIRECT MODE) the program will execute or 
          'run' It can still accept input from the keyboard if the program is 
          written so to do, as you will have seen in the program previously 
          presented, where you were asked to make a choice by typing Y or N, 
          pressing RETURN etc. 

              When you begin to get used to BASIC you will find that all modes 
          work together in a very natural way, and you will use the particular 
          mode required without thinking about it too much. However it is as 
          well to realise that there are these different ways in which BASIC 
          works from the outset. BASIC programs in general are intended to be 
          used solely in PROGRAM MODE but this course employs a different and 
          novel principle. You are constantly invited to view the 'Works' so 
          as to see what makes it tick and you will be using DIRECT MODE in 
          it's various sub-modes quite a lot to do this and to skip about the 
          program. You will be given clear instructions at all times to enable 
          you to do this, but in a short time you will pick up the simple 
          principles in the best possible way, by use.

          End of file INTRO.C   
time you will pick up the simple 
          principles in the best possible