integer nvar
    character*48 name1
      character*4 extension
      character*196 number
      character*48 num1,num2,num3,num4
    character*18  corname1,form

      num1='010203040506070809101112131415161718192021222324'
      num2='252627282930313233343536373839404142434445464748'
      num3='495051525354555657585960616263646566676869707172'
      num4='737475767778798081828384858687888990919293949596'
      number=num1//num2//num3//num4
    
    
    nvar=1      
    corname1= 'tab'
    extension='.dat'
    name1=corname1//number(2*nvar-1:2*nvar)//extension

请教一下这段程序的含义: [b]number(2*nvar-1:2*nvar)[/b]