Ap Computer Science Principles - Unit 1

Karel in Codehs

regular karel knows…

4 commands:

• move()

• turn_left()

• put_ball()

• take_ball()

rows:

columns:

streets

avenues

a function

a way to teach karel a new word

def name of function ():

indent + command

why do we use functions?

• break program into smaller parts

• make the program easier to understand

naming your function

• start with a letter, no spaces

• snake_case

  • lowercase and use underscore

• start with an action word and should sound like a command

top down design

breaking a big problem down into smaller parts

• helps to solve complicated problems

• allows to collaborate and split tasks

comments

• break down your problem

• make your code clear to others

• multi-line: ‘‘‘comment’’’

• single line: #comment

• preconditions: assumptions we make, and what must be true

• postconditions: what should be true after the function is called

abstraction

managing complexity by “abstracting away” info and details

• to focus on more relevant details

SuperKarel

two new functions:

• turn_right()

• turn_around()

API

application programming interface

• is a set of tools for building programs

For loops

• repeat a code for a fixed number of times

  • for i in range(count):

    • code to execute

if statements and conditionals

• a function that returns a true/false answer

  • if condition:

    • code

if/else statements

these statements let karel handle diffferent types of worlds

if conditions:

# code if condition is true

else:

# code to run otherwise

while loops

allows us to repeat a section of code as long as it is true

• while condition:

  • # code to execute while condition is true

control structures

• ask questions

• repeat code

debugging strategies

• attention to detail

• even smaller syntax error could be a problem

• question all your code

• small errors

  • typos in variable names

  • syntax, loops, if statements

  • code that isn’t what you meant

  • mix-ups

debugging with error messages

syntax error:

runtime error:

logic error:

program doesn’t start running

program starts but then crashes

program starts, but doesn’t do what you want

algorithms

self-contained, step by step set of instructions

programs

implementation of algorithms into a computer

3 building blocks

sequencing:

iteration:

selection:

step by step instructions in the order they are given

repetition of instructions a specified number of times'

using a condition to determine which part is executed

pseudocode

writing out the algorithm in english- like code to help us figure out how to write the program

parameters

inputs into functions

• paint(color[‘red’])

• color_is(color[‘red’])