PL/I (Computer program language) 30 Structured programming 6 Computer programming 5 PL/C (Computer program language) 4 Data processing 3 Library science 2 ALGOL (Computer program language) 1 Ada (Computer program language) 1 Assembler language (Computer program language) 1 Automation 1 Business 1 COBOL (Computer program language) 1 Compiling (Electronic computers) 1 Computer algorithms 1 Data structures (Computer science) 1 Debugging in computer science 1 FORTRAN (Computer program language) 1 FORTRAN IV (Computer program language) 1 File organization (Computer science) 1 GASP (Computer program language) 1 Handbooks, manuals, etc 1 Information science 1 Libraries 1 PL/ZERO (Computer program language) 1 Pascal (Computer program language) 1 Pl/0 (computer Programme Language) 1 Programming languages (Electronic computers) 1 Standards 1