section_heading: 1966: FORTRAN 66
paragraph_text: FORTRAN 66's equivalent of the <code>for</code> loop is the <code>DO</code> loop. The syntax of Fortran's <CODE>DO</CODE> loop is: DO label counter=start, stop, step label naredbe Example: PROGRAM MAIN SUM SQ=0 DO 101 I=1,9999999 IF (SUM SQ.GT.1000) GO TO 109 SUM SQ=SUM SQ+I**2 101     CONTINUE 109     CONTINUE END The fortran DO loop caused an orbit computation error in a Mercury flight, and was long suspected to have caused the crash of the Mariner 1 space rocket on 22 July 1962 - C.A.R. Hoare, in particular a missing comma in the wrong place can drastically alter the meaning of the loop. Example: DO 101 I=1.9999999 101     CONTINUE Because of the peculiar feature of fortran that spaces are not significant, this is interpreted as a single assignment to the (probably undeclared) variable <code>DO101I</code>. In the subsequent FORTRAN 77 specification an additional comma was required in the <code>DO</code> loop syntax.