OS
This mode allows the CPU to run any instruction and access any memory location, and is where OS services run.
This is a software mechanism, used to ensure that only one thread can execute a critical section of code at a time.
What is a Mutex Lock?
This protocol is responsible for translating human-readable hostnames into IP.
What is DNS?
In a shell script, "$*" is used for this purpose
What is accessing all command-line arguments passed to the script?
This type of software development tool (e.g., Git, SVN) is essential for team collaboration, tracking changes, and managing different versions of code.
What is Source Control?
This is the OS subsystem responsible for deciding which process to run next and performing context switches.
What is the Process Scheduler?
This term describes a data structure or function that can be safely used by multiple threads concurrently without causing issues like race conditions.
What is Thread-Safe?
This transport protocol provides reliable, connection-oriented, full-duplex stream communication.
What is TCP?
This system call is used by a parent process to create a new child process that is initially a copy of the parent.
What is fork()?
This testing practice involves writing tests before writing the actual code to implement a feature.
What is "Code unit-test first"?
This type of scheduling allows a running process to be interrupted by the OS, typically after a time quantum expires, to allow other processes to run.
What is Preemptive Scheduling?
This synchronization primitive is initialized with a counter and allows a specified number of threads to pass
What is semaphore?
This technology allows multiple computers on a private network to share a single public IP address and often acts as a firewall.
What is NAT?
When implementing wildcard expansion like *.c, this POSIX function can be used to compile a wildcard pattern into a regular expression.
What is regcomp()?
This design pattern encapsulates a command request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
What is the Command Pattern?
Describe the primary contents of an entry in the Process Table.
What is PID, command & arguments, environment variables, current directory, owner (UID), stdin/stdout/stderr, list of memory mappings, list of open files, and for each thread: PC, registers, stack, and state?
When two or more threads are blocked forever, each waiting for a resource held by another thread in the cycle.
What is a deadlock?
What are:
The local IP address
The subnet mask
The default router
The default DNS server
Describe the implementation of subshells.
What is: 1. The parent shell creates two pipes (e.g., pin for input to the subshell, pout for output from the subshell). 2. The parent forks a child process. 3. The child process redirects its standard input to read from pin[0] and its standard output to write to pout[1]. It closes unused pipe ends. 4. The child process then often executes an instance of the shell itself (e.g., via /proc/self/exe) to parse and run the command string within the backticks. 5. The parent shell writes the command string (e.g., "cat a.out") followed by a newline and often an "exit" command to pin[1] and closes pin[1]. 6. The parent shell reads the output of the subshell command from pout[0] into a buffer until EOF. 7. This buffered output is then substituted as an argument (or arguments, if split by spaces) into the original command line.
All code must have uni tests
All code must pass all unit tests before integration
When a bug is found create a test.
Create acceptance tests
Explain the steps involved when a user program makes a system call, including the transition between modes and the role of the interrupt handler.
What is:
1. User program calls a library wrapper function (e.g., open() in libc).
2. Library wrapper executes a special software interrupt instruction.
3. CPU switches from User Mode to Kernel Mode.
4. The OS's system call interrupt handler is invoked.
5. The handler identifies the specific system call, validates arguments, and performs security checks.
6. The OS executes the requested service.
7. Results are returned to the library wrapper, and the CPU switches back to User Mode.
8. The library wrapper returns to the user program.
Describe how a Read/Write lock works and in what scenario it is more advantageous than a simple mutex lock.
What is: A Read/Write lock allows multiple threads to read a shared resource simultaneously (multiple readers) but ensures that only one thread can modify (write to) the resource at a time, excluding all readers and other writers. It is advantageous when read operations are much more frequent than write operations.
The process TCP uses to establish and close connections to ensure reliability
What is the three-way handshake
Explain how I/O redirection (e.g., ls -l > output.txt) and pipes (e.g., ls -l | grep myFile) are typically implemented in a shell
Any acceptable answer
Do you use source control?
Can you make a build in one step?
Do you make daily builds?
Do you have a bug database?
Do you fix bugs before writing new code?
Do you have an up-to-date schedule?
Do you have a spec?
Do programmers have quiet working conditions?
Do you use the best tools money can buy?
Do you have testers?
Do new candidates write code during their interview?
Do you do hallway usability testing?