Quote: don't live with broken windows; fix bad decisions and poor code; isolate if not enough time [»huntA_2000]

Quote: software requires a lot of maintenance because it is difficult to develop systems which are correct and capable [»millHD_1979]

Quote: despite lots of time spending tidying things, things get in a muddle by themselves [»bateG_1972]

Quote: human errors are intrinsic to being human [»parnDL2_1986]

Quote: err and err and err again, but less and less and less [»knutDE7_1989]

Quote: most software engineering research concerns new system development instead of software maintenance [»klinR2_1979]

Quote: despite the importance of software maintenance, it has second shortest chapter; even less than software cost estimation [»fairRE_1985, OK]

Quote: more resources should be spent on testing a system than on constructing the initial implementation [»stroB_1991]

Quote: software maintenance tools must account for the long tails of many usage statistics; these are critical cases that need support the most [»perrDE4_1998]

Quote: inspections make code easier to understand and change; 60% of issues concerned maintainability; e.g., coding standards, comments, portability, documentation [»siyH12_2001]

Quote: the most expensive errors are maintenance errors; the top 3 due to changing one digit [»weinGM8_1983]

Quote: small changes have high error rates, because they are not taken seriously [»weinGM8_1983]

Quote: a maintenance programmer is more like a brain surgeon than a janitor [»weinGM8_1983]

Quote: a function interface should lead to correct code; avoid multiple returns, error values, and multipurpose functions; allow strong argument validation [»maguS_1993]

Quote: Y2K happened because data processing implemented existing practices w/o date abstractions [»huntA_2000]

Quote: 20% of maintenance cost due to procedure size; optimal size was 44 executable statements [»bankRD11_1993]

Quote: 12% of maintenance cost due to long goto statements to other COBOL paragraphs [»bankRD11_1993]

Quote: change is the primary agent of faults; large, recent changes are the most likely to fail; frequency of change is a better predictor of faults than size of module or number of developers [»eickSG1_2001]

Quote: adaptive changes add new functionality or supported environments, corrective changes fix faults, perfective changes and reengineering improves software maintenance [»eickSG4_2002]

Quote: software maintenance is really evolution since it is changing a system's attributes and characteristics [»lehmMM11_1982]

Quote: modularity decays; in 1989, the change history clearly separated two clusters of modules; by 1996, these clusters had broken down [»eickSG1_2001]

QuoteRef: brooFP_1975 ;;123 Pascal: "Things are always at their best in the beginning" or CS

Quote: software maintenance consists of enhancements (60%), adaptations (20%), and corrections (20%) [»fairRE_1985]

Quote: software maintenance consists of understanding the existing software, modifying it, and revalidating it [»boehBW12_1976]

Quote: the main activity of programming is the integration, modification, and explanation of existing programs [»winoT7_1979]

Quote: DRY--don't repeat yourself; every piece of knowledge must have a single representation in a system; knowledge changes too fast to keep multiple copies consistent [»huntA_2000]

Quote: since a successful program will be read more often than written, review and maintenance are at least as important as design [»parnDL12_1994]

Quote: software maintenance requires good documentation [»roycWW8_1970]

Quote: maintenance programmers either systematically learn how a program behaves or learn the system as-needed; the former does better [»littDC12_1987]

Quote: systematic maintenance programmers perform, by hand, extensive symbolic execution of the data flow paths between subroutines

Quote: with a large user base, most field software failures are rediscoveries of previously reported problems [»leeI6_1996]

Quote: a rediscovery of a previously reported problem wastes service resources

Quote: diagnosed 80% of previously discovered software failures with procedure call traces and other code-oriented symptoms [»leeI6_1996]

Quote: enhanced the diagnosis of previously discovered software failures with predefined error values for certain data items

Quote: refactoring takes time and may require throwing out perfectly good code; used for new requirements under extreme programming [»berrDM10_2002]

Quote: transform source code into XML for re-engineering and migration; represents all or part of the abstract syntax tree for multiple languages; expands text six-fold [»mcarG10_2002]

Quote: refactoring is redesign of existing code; fix now instead of later; started with Smalltalk [»huntA_2000]

Quote: a refactoring browser can split up long routines, rename methods and variables, move code with drag and drop; e.g., Brant [»huntA_2000]

Quote: used points-to analysis for type consistency; given a type change, determine all other objects whose type needs to change [»heinN6_2001]

Quote: every successful major piece of software will be worked on by a succession of programmers and designers, ported to new platforms, adapted to new uses, and reorganized. Must plan for multiple versions [»stroB_1991]

Quote: a typical release of the 5ESS switch is 0.5M lines of new and changed code on a base of 5M lines [»portAA6_1997]

Quote: studied maintenance of a real-time switching system; >10 million noncommented lines of C, new functions every 15 months, 3,000 software and 500 hardware developers [»perrDE7_1994]

Quote: a new feature of a real-time switching system varied from a few lines of noncommented code to 50,000 lines of noncommented code with many complex, specially designed hardware circuits

Quote: in 1989, less than 2% of changes touched multiple files; by 1996, over 5% touched multiple files [»eickSG1_2001]

Note: nothing should happen at an upgrade; everything should work as before despite many changes [»cbb_1990, OK]

Quote: maintenance and enhancement takes 40-75% of total software effort [»lienBP6_1978, OK]

Quote: it takes about three times more development resources to modify code than to create new code [»boydRE3_1984]

Quote: system testing, enhancement and adaptation takes three-fourths of total life-cycle effort [»fairRE_1985]

QuoteRef: klinR2_1979 ;;36 "The problem is that most programming work entails maintaining already existing (sometimes archaic) software systems.

Quote: once the Unix network was in use, system maintainers were easily persuaded to keep it running and improve throughput [»nowiDA8_1978]

Quote: DSEE manages over a million lines of code successfully [»leblDB5_1984]

Quote: customer-reported software errors require an average of 4.5 person-days to repair [»russGW1_1991]

Quote: by 1988, Bell-Northern Research had written 15 million lines of code for telecommunication products [»russGW1_1991]

Quote: do not hesitate to throw out clumsy software and rebuild it [»mcilMD7_1978]

Quote: 80% of software maintenance on 2% of system; so rewrite that 2%; large reduction in overall maintenance effort [»pariG_1980]

Quote: contract requirement: 90% of bebugged errors fixed in half an hour or less [»pariG_1980]

Quote: main obstacle to changing Multics was updating system documentation [»corbFJ_1979]

Quote: with the software life cycle, changes occur reluctantly and in large packets [»mccrDD4_1982]

Quote: in large systems under maintenance, percentage of coding errors to design errors increased; averaged 40:60 for code:design [»boehBW12_1976, OK]

Quote: software repair should be assigned to those with maximum system overview and insight [»belaLA_1979]

Quote: law of conservation of familiarity: the size of each release of an evolving program will be statistically invariant [»lehmMM9_1980]