Embedded C Online Test

Consider the following logic box. There are three inputs A, B, C and three outputs not A, not B and not C (not A = !A, not B = !B, not C = !C).

Is it possible to achieve the expected outputs from the inputs using:

- Only AND and OR gates
- Just two (2) NOT gates
- No NAND, NOR, XOR, or XNOR gates

Review the following Embedded Systems code and memory map of 16-bit microcontroller:

Here are the specifications of the microcontroller:

- The stack grows from area D, whereas the program and static variables are stored in area C
- ‘int’ in the system is a 16-bit number
- There is no operating system and no memory protection
- The program is compiled and loaded into area C

Pick the correct statements:

A: first_var, second_var and input will be in area D
B: first_var and second_var will be in area C, input will be in area D
C: If the contents of 0x0010 at the start of the program is 7, the program will print 0 and exit
D: If the contents of 0x0010 at the start of the program is 42, the program will print 0 and exit
E: If the contents of 0x0010 at the start of the program is 42, the program will overflow the stack overwriting the program and static variables region
F: If the program overflows and overwrites the program and static variables region, arbitrary data is executed as if it is the program, causing unpredictable results

Review the following Embedded Systems code:

Here’s the specification for the program:
- first_var and second_var are global variables shared among several threads
- first_lock and second_lock are mutex locks that protect access to first_var and second_var
- Reads and writes to variables first_var and second_var are not guaranteed to be atomic
- No locks must be acquired unnecessarily
- Acquire second_var lock first before acquiring first_var lock by any thread that is going to use both first_var and second_var

Assume that if a thread attempts to acquire a lock it already holds, then it is immediately granted the lock. Pick the correct statements:

A: The provided code does not meet the specification completely since second_lock is not acquired before acquiring first_lock for procedure 'foo'

B: Replacing foo with logic of foo1 makes sure locks are not acquired unnecessarily and  second_lock is acquired before acquiring first_lock

C: Replacing foo with logic of foo1 makes sure second_lock is acquired before acquiring first_lock but there are cases when second_lock is acquired unnecessarily (when first_var < input)

D: Replacing foo with logic of foo2 makes sure locks are not acquired unnecessarily

E: Replacing foo with logic of foo2 is optimized version of foo1 but there are cases when second_lock is still acquired unnecessarily (when first_var value changes from the time ‘res’ value is computed and by the first_lock is acquired again.

Check the following three C functions:

Which among these will likely cause issues with pointers?

What is the output of the following C code?

What is the output of the following C code?

We want to register students for the next semester. All students have a receipt which shows the amount pending for the previous semester. A positive amount (or zero) represents that the student has paid extra fees, and a negative amount represents that they have pending fees to be paid. The students are in a queue for the registration. We want to arrange the students in a way such that the students who have a positive amount on the receipt get registered first as compared to the students who have a negative amount. We are given a queue in the form of an array containing the pending amount.

For example, if the initial queue is [20, 70, -40, 30, -10], then the final queue will be [20, 70, 30, -40, -10]. Note that the sequence of students should not be changed while arranging them unless required to meet the condition.

⚠️⚠️⚠️ Note:
- The first line of the input is the length of the array. The second line contains all the elements of the array.
- The input is already parsed into an array of "strings" and passed to a function. You will need to convert string to integer/number type inside the function.
- You need to "print" the final result (not return it) to pass the test cases.

For the example discussed above, the input will be:
5
20 70 -40 30 -10

Your code needs to print the following to the standard output:
20 70 30 -40 -10

A manager hires a staff member to keep a record of the number of men, women, and children visiting the museum daily. The staff will note W if any women visit, M for men, and C for children. You need to write code that takes the string that represents the visits and prints the count of men, woman and children. The sequencing should be in decreasing order. 

Example:

Input:
WWMMWWCCC

Expected Output: 
4W3C2M

Explanation: 
‘W’ has the highest count, then ‘C’, then ‘M’. 

⚠️⚠️⚠️ Note:
- The input is already parsed and passed to a function.
- You need to "print" the final result (not return it) to pass the test cases.
- If the input is- “MMW”, then the expected output is "2M1W" since there is no ‘C’.
- If any of them have the same count, the output should follow this order - M, W, C.