SECTION A - PRIMER                                  FILE PRIMER.A
                                   SCREEN DISPLAY
                                   **************

              It is possible to write a program where nothing appears on the 
          screen, but this is not very productive. In most programs you will 
          want to see the results of your labours shown on the screen and in a 
          pleasing and easy to understand format. This is your chance to use 
          your artistic skills to achieve a good layout. Everybody has their 
          own idea on this. I prefer a fairly plain layout, and this probably 
          reflects my engineering background. Others like to surround each 
          heading in a neat box, and use plenty of stars and other symbols to 
          decorate the screen.  In this section we find out how to write to 
          the screen and begin to see how to position text where we wish it to 
          go. 
          PRINT  This command is used to write to the screen. For example, 
          =====  PRINT "hello " is a single line in a program which will print 
          the word  hello   on the screen. The computer recognises the word 
          PRINT as a command and will print numbers, letters or symbols which 
          appear after it provided that they are properly presented. For 
          strings of letters or other symbols this means that they must be 
          enclosed in double quotes as shown. If treated in the same way, 
          numbers will print exactly as typed and BASIC will regard them 
          simply as a string like any other.
               Numbers will print without quotes and in this case can be used 
          to perform arithmetic. This is an important point; for example PRINT 
          " 6+4 " will print 6+4 on the screen, whereas PRINT 6+4 will print 
          10, the answer to the sum. In the listing which follows we shall see 
          how to use this to write complete sums.   
              A space is as much a character to your computer as any other, 
          and we can make use of this to improve layout, perhaps putting 
          spaces between words e.g PRINT "Monday      Tuesday     Wednesday" 
          when it will print exactly as shown including the spaces.
              One character that will not print between double quotes is the 
          double quote , which is hardly surprising, as the computer sees it 
          as a command in itself. There is a way of overcoming this as we 
          shall see later, but for the present a simple solution is to use 
          single quotes, as PRINT "The boy said 'Hello' and walked on "
              Finally , PRINT used on it's own will print a complete blank 
          line and one often uses lines such as  10 PRINT:PRINT "Hello"  where 
          the first PRINT simply forms a blank line to improve layout. Note 
          the colon (:) between the PRINT commands, necessary to separate 
          individual commands. Punctuation marks play a big part in 
          programming!

          PRINT TAB(10)  This command is used to start printing part-way 
          =============  across the screen instead of from the side of the 
          screen, the figure in brackets representing the distance from the 
          edge in columns. In normal useage the PCW screen is 90 columns 
          across and TAB(10) tells the computer to start printing at column 
          10. This is useful when printing central headings, or indenting 
          etc., but can fail if the TAB number is too large for the job in 
          hand. It is best used by trial and error, later guided by 
          experience. 

          ZONE  Zone printing is used to equally space numbers, words etc. 
          ====  across the screen.If no zone command is specified the default 
          setting is to print 6 columns across. For example, if we print :

              30 PRINT 23,34,21,7,90,56  (note the commas) then when run these 
          figures would be printed equally spaced across the screen. It is 
          easy to see that several lines like this would print columns of 
          figures, so that a table could be constructed. Words can be treated 
          in the same way, so headings could be added to each column. But 
          suppose we didn't want 6 columns but only 3 ?.
              The standard setting for the PCW screen has 90 columns across 
          and the zone default setting is ZONE(15) so 90 divided by 15 = 6, 
, 
          the default number of columns. If we use the command ZONE(30) then 3 
          columns will be printed ; 90 divided by 30 = 3 . The same principle 
          applies for all numbers. Some interesting results can be obtained by 
          experiment. 
               Once the ZONE command has been made it will stay in force until 
          a new ZONE setting is made or until a new program is loaded, when it 
          reverts to the default setting.
              The listing which follows illustrates the uses of PRINT ,     
          PRINT TAB( ) and ZONE. Please look for and follow the instructions 
          for running the program and don't be afraid to experiment, as this 
          will speed up the learning process as well as adding a great deal of 
          interest. If you're not sure what to do reread the INTRO section on 
          editing.

          END OF FILE PRIMER.A
           
If you're not sure what to do reread the INTRO section on 
          editing.

          END O