eca00000ff23fe0080666001f70
^1|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|

^2   B E G I N N E R S '   C O R N E R -

^2                                    B A C K   T O   B A S I C S .

^1|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|

^7 In the last Issue of Totally Amos, we took a look at variables, this
^7time  we'll  have  a  look  at  loops with the help of The Beginner's
^7Programming  Handbook,  (By  Usbourne Books) and the Easy Amos manual
^7(because it's easier for a non programmer like me to understand!)

^6 Loops  are  a way of gettong the computer to do things over and over
^6again without you having to tell it each time.

^7 There  are  a  few types of loops in Amos, let's start with one that
^7pops up everywhere - the FOR NEXT loop.

^6 An example is usually the best method of explaining something, so we
^6have  decided  that  we  want  to print the words TOTALLY AMOS on the
^6screen 10 times.

^6 We could use the following routine:-

^2Print"TOTALLY AMOS" 
^2Print"TOTALLY AMOS" 
^2Print"TOTALLY AMOS" 
^2Print"TOTALLY AMOS" 
^2Print"TOTALLY AMOS" 
^2Print"TOTALLY AMOS" 
^2Print"TOTALLY AMOS" 
^2Print"TOTALLY AMOS" 
^2Print"TOTALLY AMOS"
^2Print"TOTALLY AMOS" 

^6 But  that  is  very  repetative,  and  imagine  if  you needed to do
^6something 1000 times!

^7 In  a  FOR  NEXT Loop, we can set a counter which will detirmine the
^7number of times that an instruction is carried out, this is set as:-

^2For T = 1 To 10      ^6----- T acts as a counter, it tells the computer
                           ^6to  do something 10 times, the computer is
                           ^6told  that this counter is to count from 1
                           ^6to 10. Every  time  the program comes back
                           ^6here, 1 is added  to  T, the program stops
                           ^6when the counter reaches 10.

^7 Now we want to tell the computer what we want printed.

^2A$ = "TOTALLY AMOS"  ^6----- A$ is a string variable which we are using
                           ^6to  store  the  words  "TOTALLY  AMOS". By
                           ^6storing it in a variable, we would be able
                           ^6to  use  it  later  in the program just by
                           ^6calling A$. 

^7Here we tell the program to print.

^2Print A$             ^6----  We are telling  the  computer to print the
                           ^6words  stored  in  A$. This is what we are
                           ^6telling the computer to do 10 times.

^7Now that's been done, what's next?

^2Next T               ^6----  This  tells the computer to go back to the
                           ^6first  line  and carry out the instruction
                           ^6again.

^7 A  more  complicated  FOR  NEXT  loop is a Nested Loop.  This simply
^7means  that one FOR NEXT loop is tucked inside another FOR NEXT loop.
^7This means that you can do 2 things at once.

^7Let's look at this example:-

^2 o    -    For I = 2 To 12
^2 u   |
^2 t   |     For J = 1 To 12            _
^2 e   |                                 |
^2 r   |     Print J;"Times ";I;"=";J*I  |  Inner Loop
^2     |                                 |
^2 l   |     Next J                     _|
^2 o   |
^2 o   |_    Next I
^2 p
                                
^7 The  counter  in  the  outer loop, I, is counting from 2 to 12.  The
^7inner counter, J, counts from 1 to 12.

^7 This means that each time I counts 1, J counts from 1 to 12 before I
^7goes on to count another one.

^2 ie  I = 2       J = 1
^2                    2
^2                     3
^2                     4 and so on to 12

^2     I = 3       J = 1
^2                     2
^2                     3
^2                     4 and so on

^2  Print J;"Times ";I;"=";J*I

^7 This  line  tells  the  computer  to  print  the current value of J,
^7followed by the word "Times" (NB inverts ") then the current value of
^7I,  followed  by  the  character  `='  and  finally  the  result of J
^7multiplied  by  I.   The  semi-colon tells the computer that there is
^7something  more  to  print  before  going  on to the next part of the
^7program.

^6 Have you guessed what this program will print?

^6 It will, in fact print out the times tables from x2 up to x12.

^6 Broken down this is done as follows:-

^6 I = the number of the times table

^6 J = the numbers from 1 to 12

^7 The tables are printed in order as a long list, 

^2      1 Times 2 = 2
^2      2 Times 2 = 4
^2      3 Times 2 = 6
^2      4 Times 2 = 8 etc
 
^2 Then 1 Times 3 = 3
^2      2 Times 3 = 6
^2      3 Times 3 = 9
^2      4 Times 3 = 12 etc

^2 All the way up to 12 Times 12 = 144

^6 Can  you  see how the outer loop (I) only increments after the inner
^6loop (J) has run from 1 to 12?

^7 One  rule  to  remember is that both parts of the inner loop MUST be
^7INSIDE the outer loop, if not, you'll get an error message.

^2 ie For I....
^2    For J....
^2    Next J
^2    Next I

^1|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|

^4 If you have a Basic Blind Spot, please write and let us know so that
^4we  can  try  and help.  We hope that you can see from this series of
^4Basic  Basic,  that  nothing  is  too  trivial, it is all too easy to
^4assume  that  `everyone  must  know that!' The beginner's bits in the
^4last  2  issues  of  TA were inspired by Amos users who suffered such
^4blind spots.  Let's hope that these articles have helped.

^1|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|
\