be changed to improve efficiencybut this book is mostly concerned with getting programs to work with the least amount of effort on your part what is programmingtelevision shows and films often show programmers furiously typing cryptic streams of and on glowing screensbut modern programming isn' that mysterious programming is simply the act of entering instructions for the computer to perform these instructions might crunch some numbersmodify textlook up information in filesor communicate with other computers over the internet all programs use basic instructions as building blocks here are few of the most common onesin english"do thisthen do that "if this condition is trueperform this actionotherwisedo that action "do this action exactly times "keep doing that until this condition is true you can combine these building blocks to implement more intricate decisionstoo for examplehere are the programming instructionscalled the source codefor simple program written in the python programming language starting at the topthe python software runs each line of code (some lines are run only if certain condition is true or else python runs some other lineuntil it reaches the bottom passwordfile open('secretpasswordfile txt' secretpassword passwordfile read( print('enter your password 'typedpassword input( if typedpassword =secretpasswordy print('access granted' if typedpassword =' 'print('that password is one that an idiot puts on their luggage 'elseprint('access denied'you might not know anything about programmingbut you could probably make reasonable guess at what the previous code does just by reading it firstthe file secretpasswordfile txt is opened uand the secret password in it is read thenthe user is prompted to input password (from the keyboardw these two passwords are compared xand if they're the samethe program prints access granted to the screen nextthe program checks to see whether the password is and hints that this choice might not be the best for password if the passwords are not the samethe program prints access denied to the screen introduction xxix