Life Critical Standards: Fill & Download for Free

No, compilers are not the hardest kind of software to develop. The hardest kind of software to develop is real-time, high performance, life critical software controlling physical devices.When I was an undergrad it was common for 3rd year students to develop a Pascal compiler during a single semester course.Compilers break down into a front end and back end.The front end takes in the source code, tokenizes it, parses the tokens, and generates an internal representation of the result, usually an abstract syntax tree. Challenges in the front end include meaningful error output and unambiguously parsing the input. For some languages this is easy: the BNF grammar for Pascal fits on a couple pages. Pascal - Syntax in BNF Notation Contrast this with C++ which is unbelievably difficult to parse. (I see this as a major weakness of the language.) Is there a standard C++ grammar?The back end takes the abstract syntax tree and translates it to machine code that can be executed on the target architecture. Creating a basic back end is tedious but relatively simple. It becomes difficult when you start trying to optimize, especially with multiple dispatch, speculative execution, multiple cores, cache coherency… Correctly optimizing the output requires picayune review of the processor data sheet and a lot of analysis.Real-time, high performance, life-critical software controlling physical devices is hard because:Real-time means you must have deterministic performance for all conditions. You do not want your jet plane’s autopilot to behave erratically in the rain. Real-time + physical devices means you generally cannot use a breakpoint to debug the program: that CAT scan machine is going to keep pumping X-rays while you step into a function!High-performance in this context means you are close to the limit of what the processor or bus can do; you are limited in the logging you can output without loading the system such that it fails to achieve real-time.Life-critical means that people may die if the software fails to perform. I worked at a Wall Street firm and, in hushed tones, they emphasized their software error rate had to be less than one in a million. Inappropriately I laughed: the last place I worked was on emergency radio communications systems, where we validated error rates to less than one in a billion!Physical devices exhibit all kinds of unexpected behavior: stiction, mechanical resonance including sub-harmonics, wear, aging, temperature.My mother wanted me to be a medical doctor. I didn't want to do that because I didn't want to have a bad day and kill someone. Funny, now I work in life critical software where a bad day could kill many people. And I am acutely aware of that.

I wouldn’t get on an airplane built to the same standards as most business software… but you wouldn’t pay for business software built to the same standards as the avionics in an airplane either, so it works both ways.Software IS engineering, it’s just that a good engineer optimises for a particular target… and reliability is expensive, so when optimising for cost you go for merely tolerable reliability. But in life critical systems, you can do so much more, at a price.

Ladies and Gentlemen of Quora, I give you Ida TarbellShe was the daughter of an independent oil producer named Frank Tarbell whose business was threatened by unfair trading practices, and monopoly by John D. Rockefeller Sr. and his oil company called Standard Oil.Frank Tarbell was an independent oilman crushed in the massacre. His daughter Ida, 14 years old at the time, remembered years later how her father’s partner killed himself and how their once-prosperous life came tumbling down as Frank was forced to mortgage their home. Rockefeller went on to buy refining centers in Pittsburgh, Philadelphia, Baltimore, New York, and elsewhere. His secret deals with the railroads, which gave him favorable rebates, assured his domination.[1][1][1][1]With fire in her heart, almost thirty years later, she wrote a 19 part book called ‘The History of the Standard Oil Company' exposing their unfair and illegal practices. She, a rather obscure journalist was going up against one of the richest men and most powerful companies in America.Her reports ended up bringing a wave of public criticism. Standard Oil was found to be in violation of the Sherman Antitrust Act by the Supreme Court and was broken up.[2][2][2][2]Ida Tarbell gave rise to a new style of investigative journalism sometimes referred to as muckraking.If you don't call that getting the last laugh then I don't know what is.Footnotes[1] 10 Disturbing Exposes That Transformed Society - Listverse[1] 10 Disturbing Exposes That Transformed Society - Listverse[1] 10 Disturbing Exposes That Transformed Society - Listverse[1] 10 Disturbing Exposes That Transformed Society - Listverse[2] http://wiki/The_History_of_the_Standard_Oil_Company[2] http://wiki/The_History_of_the_Standard_Oil_Company[2] http://wiki/The_History_of_the_Standard_Oil_Company[2] http://wiki/The_History_of_the_Standard_Oil_Company