AP Computer Science Principles Practice Exam Notes

Exam Content and Format

• The AP Computer Science Principles Exam has two parts:
  • Create performance task (at least 12 hours of class time).
  • End-of-course AP Exam: 2 hours, 70 multiple-choice questions.

Administering the Practice Exam

• Instructions for administering the practice exam are provided.
• Exam materials needed: test booklets and answer sheets.
• Instructions for students:
  • 2 hours to answer 70 multiple-choice questions.
  • Questions 1-62: select the single best answer.
  • Questions 131-138: select the two best answer choices.
  • Total score based only on the number of questions answered correctly. No points deducted for incorrect or unanswered questions.
  • Eliminate choices when unsure and select the best among remaining.
  • Checking work is allowed if time permits.
  • Programming reference materials are located at the front of the exam.
  • Reference materials provide instructions and explanations to help understand the format and meaning of the questions.

Reference Materials

• Programming instructions use four data types: numbers, Booleans, strings, and lists.
• Instructions may include:
  • Assignment, Display, and Input
  • Arithmetic Operators and Numeric Procedures
  • Relational and Boolean Operators
  • Selection
  • Iteration
  • List Operations
  • Procedures and Procedure Calls
  • Robot

Assignment, Display, and Input

• Assignment
  • Text: a ← expression
  • Block: [Block diagram of assignment]
  • Evaluates the expression and assigns a copy of the result to variable a.
• Display
  • Text: DISPLAY(expression)
  • Block: [Block diagram of display]
  • Displays the value of the expression, followed by a space.
• Input
  • Text: INPUT()
  • Block: [Block diagram of input]
  • Accepts a value from the user and returns the input value.

Arithmetic Operators and Numeric Procedures

• Arithmetic Operators
  • Text and Block: a + b, a - b, a * b, a / b
  • Perform arithmetic on a and b.
  • Example: 17 / 5 evaluates to 3.4.
  • Order of operations applies.
• MOD Operator
  • Text and Block: a MOD b
  • Evaluates to the remainder when a is divided by b.
  • a is an integer >= 0, b is an integer > 0.
  • Example: 17 MOD 5 evaluates to 2.
  • Precedence is the same as * and /.
• RANDOM Procedure
  • Text: RANDOM(a, b)
  • Block: [Block diagram of random]
  • Generates and returns a random integer from a to b (inclusive).
  • Each result is equally likely.
  • Example: RANDOM(1, 3) could return 1, 2, or 3.

Relational and Boolean Operators

• Relational Operators
  • Text and Block: a = b, a ≠ b, a > b, a < b, a ≥ b, a ≤ b
  • Test the relationship between two variables, expressions, or values.
  • Evaluates to a Boolean value (true or false).
  • Example: a = b is true if a and b are equal, otherwise false.
• NOT Operator
  • Text: NOT condition
  • Block: [Block diagram of not]
  • Evaluates to true if condition is false; otherwise, evaluates to false.
• AND Operator
  • Text: condition1 AND condition2
  • Block: [Block diagram of and]
  • Evaluates to true if both condition1 and condition2 are true; otherwise, evaluates to false.
• OR Operator
  • Text: condition1 OR condition2
  • Block: [Block diagram of or]
  • Evaluates to true if condition1 is true, or if condition2 is true, or if both are true; otherwise evaluates to false.

Selection

• IF Statement

  • Text:

  IF(condition) {
      <block of statements>
  }
  

  • Block: [Block diagram of if]
  • Code in the block of statements is executed if the Boolean expression condition evaluates to true; no action if condition is false.

• IF-ELSE Statement

  • Text:

  IF(condition) {
      <first block of statements>
  } ELSE {
      <second block of statements>
  }
  

  • Block: [Block diagram of if-else]
  • Code in the first block is executed if condition is true; otherwise, code in the second block is executed.

Iteration

• REPEAT n TIMES

  • Text:

  REPEAT n TIMES {
      <block of statements>
  }
  

  • Block: [Block diagram of repeat n times]
  • Code in the block of statements is executed n times.

• REPEAT UNTIL (condition)

  • Text:

  REPEAT UNTIL(condition) {
      <block of statements>
  }
  

  • Block: [Block diagram of repeat until]
  • Code in the block of statements is repeated until the Boolean expression condition evaluates to true.

List Operations

• If a list index is out of bounds (less than 1 or greater than the length of the list), an error occurs and the program terminates.

• List Creation

  • Text: aList ← [value1, value2, value3, ...]
  • Block: [Block diagram of list creation]
  • Creates a new list with the given values at indices 1, 2, 3, … and assigns it to aList.

• Empty List Creation

  • Text: aList ← []
  • Block: [Block diagram of empty list creation]
  • Creates an empty list and assigns it to aList.

• List Copy

  • Text: aList ← bList
  • Block: [Block diagram of list copy]
  • Assigns a copy of list bList to list aList.
  • Example: If bList is [20, 40, 60], then aList will also be [20, 40, 60].

• Access Element at Index

  • Text: aList[i]
  • Block: [Block diagram of access element]
  • Accesses the element of aList at index i.
  • The first element is at index 1 (aList[1]).

• Assign Value from List

  • Text: x ← aList[i]
  • Block: [Block diagram of assign value from list]
  • Assigns the value of aList[i] to the variable x.

• Assign Value to List

  • Text: aList[i] ← x
  • Block: [Block diagram of assign value to list]
  • Assigns the value of x to aList[i].

• Assign Value from List to Another Index

  • Text: aList[i] ← aList[j]
  • Block: [Block diagram of assign value list to another index]
  • Assigns the value of aList[j] to aList[i].

• Insert Value

  • Text: INSERT(aList, i, value)
  • Block: [Block diagram of insert value]
  • Shifts values at indices >= i one position to the right.
  • Increases the length of the list by 1.
  • Places value at index i in aList.

• Append Value

  • Text: APPEND(aList, value)
  • Block: [Block diagram of append value]
  • Increases the length of aList by 1.
  • Places value at the end of aList.

• Remove Value

  • Text: REMOVE(aList, i)
  • Block: [Block diagram of remove value]
  • Removes the item at index i in aList.
  • Shifts values at indices > i to the left.
  • Decreases the length of aList by 1.

• Length of List

  • Text: LENGTH(aList)
  • Block: [Block diagram of length of list]
  • Evaluates to the number of elements in aList.

• For Each Item in List

  • Text:

  FOR EACH item IN aList {
      <block of statements>
  }
  

  • Block: [Block diagram of for each item in list]
  • The variable item is assigned the value of each element of aList sequentially (from first to last).
  • The code in the block of statements is executed once for each assignment of item.

Procedures and Procedure Calls

• Procedure Definition

  • Text:

  PROCEDURE procName(parameter1, parameter2, ...) {
      <block of statements>
  }
  

  • Block: [Block diagram of procedure definition]
  • Defines procName as a procedure that takes zero or more arguments.
  • The procedure contains a block of statements.
  • procName can be called as procName(arg1, arg2, ...) (where arg1 is assigned to parameter1, arg2 to parameter2, etc.).

• Procedure Definition with Return

  • Text:

  PROCEDURE procName(parameter1, parameter2, ...) {
      <block of statements>
      RETURN(expression)
  }
  

  • Block: [Block diagram of definition with return]
  • Defines procName as a procedure that takes zero or more arguments.
  • The procedure contains a block of statements and returns the value of expression.
  • RETURN may appear at any point inside the procedure, causing an immediate return to the calling statement.
  • The value returned can be assigned as result ← procName(arg1, arg2, ...).

• Return Statement

  • Text: RETURN(expression)
  • Block: [Block diagram of return]
  • Returns flow of control to the point where the procedure was called and returns the value of expression.

Robot

• If the robot attempts to move to a square that is not open or is beyond the edge of the grid, the robot will stay in its current location and the program will terminate.
• MOVE_FORWARD()
  • Block: [Block diagram of move forward]
  • The robot moves one square forward in the direction it is facing.
• ROTATE_LEFT()
  • Block: [Block diagram of rotate left]
  • The robot rotates in place 90 degrees counterclockwise (left turn).
• ROTATE_RIGHT()
  • Block: [Block diagram of rotate right]
  • The robot rotates in place 90 degrees clockwise (right turn).
• CAN_MOVE(direction)
  • Block: [Block diagram of can move]
  • Evaluates to true if there is an open square one square in the direction relative to where the robot is facing; otherwise, evaluates to false.
  • direction can be left, right, forward, or backward.