Systems and Embedded Language

C Programming Homework Help

Q: Can you help with OS assignments?

Yes. Process scheduling, virtual memory with page tables and TLB, file systems with inodes, synchronization primitives, and kernel modules for Linux. Pintos and xv6 lab support included.

Valgrind-clean solutions for systems, sockets, and memory-allocator assignments, with ownership comments on every malloc and free. The most-deducted bug in Computer Systems labs (Berkeley CS61C, CMU 15-213, U of T CSC369, Manchester COMP25212, NUS CS2106, IIT Bombay CS347) is a missing NULL check after malloc that segfaults under low-memory test inputs, the exact failure mode our tutors catch with explicit defensive programming. Verified CS graduates from EPFL Lausanne, Purdue, U of Toronto, Manchester, NUS, and IIT, starting at $20 per task, 12-hour average turnaround.

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Machine Structures

Top Course

Why C

C at the university level

Topics covered

What we tutor in C

Pointers & Memory Management

Stack vs heap allocation, malloc and free pairing, dangling pointer prevention, and Valgrind workflows for leak detection.

Data Structures (from scratch)

Linked list, BST, hash table, and heap implementations in pure C with explicit memory hygiene and adversarial test coverage.

Systems Programming (Unix/Linux)

fork, exec, wait, pipe, signal handlers, and the kernel-interface patterns CS161 / CMU 15-213 grades against POSIX conformance.

File I/O & System Calls

Implementation patterns, named pitfalls, and the autograder cases that catch them in C coursework.

Embedded Systems & Bare Metal

Implementation patterns, named pitfalls, and the autograder cases that catch them in C coursework.

Network Programming (Sockets)

Implementation patterns, named pitfalls, and the autograder cases that catch them in C coursework.

Pair C with

Operating Systems Pointers Concurrency

Full overview

C in CS curricula

C is the foundational language of systems programming. The Linux kernel, the SQLite engine, and the CPython interpreter are written in C, which is why systems courses use it as the teaching ISA for memory layout and system calls. Machine Structures sequences (Berkeley CS61C, U of T CSC258, Manchester COMP25212, NUS CS2100, IIT Bombay CS232, ETH Zurich Digital Design and Computer Architecture) use C for the linked-list and hash-table projects that surface dangling-pointer bugs Valgrind diagnoses cleanly.

Introduction to Computer Systems (CMU 15-213, U of T CSC369, Edinburgh INFR10063, NUS CS3210, IIT Delhi COL216, MIT 6.106) grade the malloc lab, the cache lab, the attack lab, and the proxy lab in C against course-specific autograders that run on Linux. Systems Programming (Stanford CS107, U of T CSC209, Manchester COMP30023, NUS CS2106, IIT Bombay CS347) covers the assembly-to-C correspondence with hand-written x86-64 alongside the C source. Operating Systems (CS162 at Berkeley, CS362 in the US, U of T CSC469, Manchester COMP30023, NUS CS3210, IIT Bombay CS347, ETH Zurich 252-0062, KAIST CS330) move to fork, exec, pipe, dup2, mmap, and pthreads for process and thread management.

Embedded courses (Purdue CS410, U of T ECE361, Manchester COMP22712, NUS CS3237, IIT Madras CS6240, ETH Zurich Embedded Systems) cover bare-metal programming on ARM Cortex-M and AVR with I2C, SPI, and UART drivers. Network programming courses (Berkeley CS168, U of T CSC358, Manchester COMP28411, Edinburgh INFR10074, NUS CS2105, IIT Bombay CS634) cover TCP and UDP socket programming with select, poll, and epoll for high-concurrency I/O. Our C tutors deliver code compiled with -Wall -Wextra -Wpedantic -fsanitize=address,undefined, every warning addressed, defensive NULL checks on every malloc, and Valgrind output showing zero leaks and zero errors.

The CSHH bench for C draws on tutors with depth in production systems C (Marcus Weber, EPFL Lausanne MS, ex-trading-desk systems engineer, pthreads and lock-free patterns) and architecture-level C (James Okafor, Purdue BS, kernel-security shop, x86-64 calling conventions and ABI).

Where Students Get Stuck

Six named C failure modes

Missing NULL check after malloc

The autograder runs under ulimit -v to force allocation failure. Programs that skip the NULL check segfault. We add if (p == NULL) return -1 (or equivalent) after every allocation and document the error path in the function header.

Off-by-one in null terminator

Allocating strlen(s) bytes instead of strlen(s) + 1 produces a string that prints correctly under most inputs and crashes on the boundary. We use snprintf with explicit buffer sizes or add an assert(buf_size > strlen(src)) check.

Use-after-free in linked list traversal

Freeing a node then dereferencing node->next is the classic bug. The fix: save node->next into a local before calling free(node). AddressSanitizer pinpoints the dereference instantly.

Double free

Calling free twice on the same pointer corrupts malloc metadata silently. We set the pointer to NULL after free, so the second free becomes a safe no-op (free(NULL) is defined).

Undefined behavior the optimizer exploited

Signed integer overflow, strict-aliasing violations, and uninitialized stack variables compile cleanly at -O0 and break at -O2. We compile with -fsanitize=undefined to surface the UB at runtime with file and line numbers.

Race conditions in pthreads

Unsynchronized access between threads passes single-threaded tests. The autograder uses -fsanitize=thread to catch the race. We identify the shared resource, add a pthread_mutex around the critical section, and verify with Helgrind.

Debugging C code step by step with breakpoints, variable inspection, and step controls

How we work

Our C approach

Clean, portable C compiled without warnings under -Wall -Wextra -Wpedantic and AddressSanitizer plus UndefinedBehaviorSanitizer. Defensive programming: NULL checks on every malloc, bounds checking on arrays, errno inspection after every system call. Every function documented with purpose, parameters, return value, and error conditions in a header comment.

Valgrind output showing zero leaks and zero errors attached to every delivery. Memory diagrams for pointer relationships and stack frames on any code exceeding 100 lines. Step 1: read the autograder spec first and identify the compiler flags.

Step 2: write the function signatures with documented ownership: who allocates, who frees, who borrows. Step 3: implement with defensive checks at every boundary. Step 4: write test cases covering NULL inputs, empty inputs, capacity-1, and adversarial sequences.

Step 5: run Valgrind and AddressSanitizer locally before delivery.

What you receive

Autograder and artifact bundle

Every C delivery ships with the .c and .h source files in the directory layout your course expects, a Makefile matching the autograder format (Berkeley CS61C, Stanford CS107, CMU 15-213, U of T CSC369, Manchester COMP25212, NUS CS2106, or institution-local), a SOLUTION.md with the design rationale and complexity analysis per function, and a CHECKLIST.md mapping each rubric item to where it is satisfied. The bundle adds a Valgrind output file (memcheck --leak-check=full --track-origins=yes), an AddressSanitizer log under -O2, and an ownership diagram (ASCII or rendered) for any pointer-heavy code exceeding 100 lines.

Where It Appears

C in University Curricula

	Course Context	CSHH Coverage
Machine Structures (Berkeley CS61C, U of T CSC258, Manchester COMP25212, NUS CS2100, IIT Bombay CS232)	Linked list and hash table projects in C surface dangling-pointer and use-after-free bugs that Valgrind diagnoses cleanly. The performance autograder rewards cache-blocked memory access patterns.	Course-specific brief
Introduction to Computer Systems (CMU 15-213, U of T CSC369, Edinburgh INFR10063, NUS CS3210, IIT Delhi COL216, MIT 6.106)	The malloc lab requires implementing free-list allocators with coalescing and splitting; the cache lab tests cache-aware access patterns. The proxy lab adds concurrent HTTP request handling with pthreads.	Course-specific brief
Systems Programming (Stanford CS107, U of T CSC209, Manchester COMP30023, NUS CS2106, IIT Bombay CS347)	Hand-written x86-64 alongside the C source for assignments on assembly-to-C correspondence. The starter codebase is C-centric with the Linux System V calling convention.	Course-specific brief
Operating Systems (Berkeley CS162, U of T CSC469, Manchester COMP30023, NUS CS3210, IIT Bombay CS347, ETH Zurich 252-0062, KAIST CS330)	fork, exec, pipe, dup2, mmap, and pthreads for process and thread management. The Pintos or xv6 lab grades a tiny kernel implementation in C with course-specific test inputs.	Course-specific brief
Unix Shell and Systems Programming (CS351 in the US, U of T CSC209, Manchester COMP30023, NUS CS2106, IIT Bombay CS347)	Unix shell with pipe chains, I/O redirection, background processes, signal handling, built-in commands, and job control using fork, exec, wait, pipe, dup2.	Course-specific brief
Embedded Systems (Purdue CS410, U of T ECE361, Manchester COMP22712, NUS CS3237, IIT Madras CS6240, ETH Zurich Embedded Systems)	Bare-metal programming with memory-mapped registers, interrupt handlers, RTOS (FreeRTOS, Zephyr), I2C, SPI, UART drivers, and cross-compilation for Cortex-M and AVR targets.	Course-specific brief

Advanced Topics

Graduate-level C we cover

Memory Allocator Design

Custom malloc/free using sbrk() or mmap(). Free list management, splitting, coalescing, boundary tags, and buddy system strategies. Performance benchmarks against libc malloc.

Network Protocol Implementation

Building protocols from RFCs: byte ordering with htonl/ntohl, serialization, state machines, timeout handling, and TCP-like reliability over UDP.

Kernel Module Development

Kernel vs user space, module init/cleanup, proc filesystem, ioctl handlers, spinlocks, and RCU (Read-Copy-Update) for lock-free data structures.

Compiler Frontend

Hand-written scanners, recursive descent parsing, AST construction, and type checking for subset languages. The CMU 15-411 compiler course is the canonical reference.

Sample Output

Idiomatic C we ship

C sample

/* Generic linked list in C with defensive checks */
#include <stdlib.h>

typedef struct Node {
    void *data;
    struct Node *next;
} Node;

Node* list_prepend(Node *head, void *data) {
    Node *new_node = malloc(sizeof(Node));
    if (new_node == NULL) return head;
    new_node->data = data;
    new_node->next = head;
    return new_node;
}

void list_free(Node *head) {
    while (head != NULL) {
        Node *tmp = head;
        head = head->next;
        free(tmp);
    }
}

IDE workspace showing C code with file tree, syntax highlighting, and minimap

Tools & Environment

Tools we use for C

GCCClangGDBValgrindAddressSanitizerstraceMakeCMakeVim/EmacsGitWireshark

Sample Projects

Recent C deliveries

Unix Shell Implementation

Pipe chains across N commands, I/O redirection with dup2, background processes with fork plus setpgid, signal handling for SIGINT and SIGTSTP, built-in commands, and job control.

Memory Allocator (malloc/free)

Explicit free list with coalescing, best-fit allocation strategy, boundary tags for O(1) coalescing, and performance benchmarks measured against glibc malloc.

HTTP/1.1 Web Server

Multi-threaded with pthreads, GET and POST handling, static file serving with sendfile, MIME type detection, persistent connections, and proper error responses.

File System Implementation

Virtual disk with inodes, direct and indirect blocks, free block bitmap, and CRUD plus mkdir supporting hierarchical directories.

Tutors who cover this language

Verified C tutors

Marcus W., MS CS

MS CS

C memory management (malloc/free discipline, valgrind traces)C++ RAII and modern ownership patterns (unique_ptr, shared_ptr, move semantics)pthreads concurrency (mutex, condvar, rwlock, race-condition isolation) +5 more

980+ assignments completed

James O., BS CS

BS CS

x86-64 assembly (System V AMD64 calling convention, SSE/AVX vector instructions)ARM64 assembly (AArch64 calling convention, NEON intrinsics)RISC-V assembly (RV32I, RV64I, M and F extensions) +5 more

620+ assignments completed

FAQ

C homework help, frequently asked

Can you help with OS assignments?

Yes. Process scheduling, virtual memory with page tables and TLB, file systems with inodes, synchronization primitives, and kernel modules for Linux. Pintos and xv6 lab support included.

Do you debug memory leaks?

Valgrind --tool=memcheck --leak-check=full --track-origins=yes plus AddressSanitizer to trace every allocation. We provide annotated reports and teach the discipline so the next leak is faster to find.

Can you help with embedded C?

Bare-metal programming with memory-mapped registers, interrupt handlers, RTOS support (FreeRTOS, Zephyr), I2C, SPI, UART drivers, and cross-compilation for ARM Cortex-M and AVR targets.

Do you help with socket programming?

TCP and UDP clients and servers, connection management, protocol state machines, and select, poll, or epoll for concurrent I/O. Includes proper EAGAIN, EINTR, and EWOULDBLOCK handling.

Can you implement data structures in C?

Linked lists, hash tables with chaining and open addressing, BSTs, heaps, and graphs with clean APIs, defensive NULL checks, proper error handling, and zero Valgrind errors.

Do you help with Makefiles?

Proper dependency tracking with gcc -MMD, separate compilation, debug and release targets, and pattern rules for portability. Also CMake for larger cross-platform projects.

Can you help build a Unix shell?

Pipe chains, I/O redirection with dup2, signal handling for SIGINT and SIGTSTP, built-in commands, and job control using fork, exec, wait, pipe, and setpgid.

Do you support cross-platform C?

Portable code for Linux, macOS, and Windows with conditional compilation (#ifdef) and abstraction layers for filesystem and threading primitives.

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