Editing TECO (text editor) (section)

==Example code==
Given a file named hello.c with the following contents:
<syntaxhighlight lang="c">
 int main(int argc, char **argv)
 {
     printf("Hello world!\n");
     return 0;
 }
</syntaxhighlight>
one could use the following TECO session (noting that the prompt is "*" and "$" is how ESC is echoed) to change "Hello" into "Goodbye":

<syntaxhighlight lang="text">
*EBhello.c$$                     Open file for read/write with backup
*P$$                             Read in the first page
*SHello$0TT$$                    Search for "Hello" and print the line (pointer placed after searched string)
    printf("Hello world!\n");    The line
*-5DIGoodbye$0TT$$               Delete five characters before pointer (ie "Hello"), insert "Goodbye", and print the line
    printf("Goodbye world!\n");  The updated line
*EX$$                            Copy the remainder of the file and exit
</syntaxhighlight>

These two example programs are a simple interchange sort of the current text buffer, based on the 1st character of each line, taken from the PDP-11 TECO User's Guide.<ref name=StdTeco/> A "[[GOTO|goto]]" and "[[structured programming|structured]]" version are shown. The second program originally had a bug that prevented the program terminating and the fixed version is used here instead.

===Example 1===
 !START! j 0aua               ! jump to beginning, load 1st char in register A !
 !CONT! l 0aub                ! load first char of next line in register B !
 qa-qb"g xa k -l ga 1uz '     ! if A>B, switch lines and set flag in register Z !
 qbua                         ! load B into A !
 l z-."g -l @o/CONT/ '        ! loop back if another line in buffer !
 qz"g 0uz @o/START/ '         ! repeat if a switch was made on last pass !

===Example 2===
 <0uz                            ! clear repeat flag !
 j 0aua l                        ! load 1st char into register A !
 <0aub                           ! load 1st char of next line into B !
 qa-qb"g xa k -l ga -1uz '       ! if A>B, switch lines and set flag !
 qbua                            ! load B into A !
 l .-z;>                         ! loop back if another line in buffer !
 qz;>                            ! repeat if a switch was made last pass !