Program to reverse a string in qbasic with explanation

cls

input"enter the string to reverse";a$

for i = 1 to len(a$)

q$=mid$(a$,i,1)

m$=q$+m$

next i 

print m$

end

                    

len(a$)  = to return the number of characters from the string

mid$(a$,i,1) = to replace a string portion with another string .

program explanation :

the program is started with the input.

then the program goes to a loop which starts from 1 and ends with the length of input.

there is the use of mid$ . why? let me give you a example : if you input a string "closure" then loop is started from 1 to length of  closure i.e 7 and mid$ takes out :

loop count                                     string

1                      c

2                      l

3                      o

4                      s

5                      u

6                      r

7                      e

after that a new string variable is created which stores in given way

if a$="ram" then

1                      p$=r

2                      p$=a

3                      p$=m

m$ where m$ is a new string

m$=a$+m$ 

so that

count                 m$

1                      r 

2                      ar

3                      mar

loop is ended and m is printed.