AP Computer Science A : Double
Study concepts, example questions & explanations for AP Computer Science A
All AP Computer Science A Resources
Example Questions
Example Question #1 :Double
What line number makes the following Python Code not execute? (1:, 2:, 3:,... represents line numbers)
1: x=[]
2: y=[]
3: z=[]
4: for i in range(10):
5: x.append(i)
6: y.append(x[i]+2*x[i])
7: z.append(x[i]+y[i]**2)
8: print(z)
9: string="The fourth element of z is "+z[3]
10: print(string)
Line 8
Line 5
Line 9
Line 6
Line 7
Line 9
When the code is executed it will produce a type error with the variable string in line 9. The variable string is trying to concatenate a string and an integer from the z array. To make the code executable, we would need to make the integer from the z array a string. We would do this by simply wrapping it in the method str(), which converts it into a string. After making the change, the following code will execute correctly.
1: x=[]
2: y=[]
3: z=[]
4: for i in range(10):
5: x.append(i)
6: y.append(x[i]+2*x[i])
7: z.append(x[i]+y[i]**2)
8: print(z)
9: string="The fourth element of z is"+str(z[3])
10: print(string)
Example Question #2 :Double
Consider the following code:
double a = 4.5, d = 4;
int b = 10,c=5;
double e = a / b + c / d - d % c;
What is the value ofeat the end of this code's execution?
有一个类型相关的错误代码。
The easiest way to work through this code is to comment on its parts. See the comments below inbold.
double a = 4.5, d = 4;
int b = 10,c=5;
/*
a / b: This is a division thatwillmaintain the decimal portion (since it has a double involved in it). 4.5 / 10 will evaluate to 0.45.
c / d: Since this has both an int and a double, it will evaluate to a double. That means that it will maintain its decimal portion as well. It is: 5 / 4 or 1.25.
d % c: Since d is 4, this kind of remainder division works just like having two integers for the modulus. 4 % 5 is just 4. (It is 0 remainder 4.)
Thus, the expression is: 0.45 + 1.25 - 4, which is -2.3.
*/
double e = a / b + c / d - d % c;
Example Question #22 :Primitive Data Types
What is the size of thefloatdata type in Java?
6 bytes (48 bits)
1 byte (8 bits)
4 bytes (32 bits)
2 bytes (16 bits)
8 bytes (64 bits)
4 bytes (32 bits)
Afloatis represented by 4 bytes (32 bits). It's comprised of 1 sign bit, 8 exponent bits, and 23 mantissa bits. An example of a floating point number in binary would be11111111111111111111111111111111. The breakdown would be[1](sign bit) [11111111](exponent bits) [11111111111111111111111](mantissa bits). All in all, that equals 32 bits.
In Java, thebyteis the only 8 bit data type. Theshortandcharare 16 bits in size. There are no 48 bit data types, as everything is in a power of 2. Thedoubleandlongare 64 bits in size.
Becausefloatshave half the number of bits asdoubles, it isn't as precise, so shouldn't be used when lots of precision is needed. It's better suited for when there are memory size concerns.
Example Question #1 :Double
Breanna想跟踪她多少葡萄eats in a day over the course of a week.
Her brother Nathan, however, wants to keep track of the average amount of grapes he eats in a day over the course of a week.
What type of variable would best be fit for what Breanna wants to keep track of? What about Nathan?
Breanna should use int
Nathan should use int
Breanna should use double
Nathan should use int
Breanna should use int
Nathan should use double
Breanna should use double
Nathan should use double
Breanna should use int
Nathan should use double
Breanna should use int because she would be counting whole numbers.
Nathan however, should use double because he will be adding up how many grapes he eats and divide by the number of days in the week.
All AP Computer Science A Resources
