intermediate · No code

C Refresher

Refresh core C concepts including pointers, arrays, strings, structs, and manual memory management. Develop safe reasoning skills for tracing memory, interpreting pointer behavior, and identifying common bugs such as leaks, dangling pointers, and out-of-bounds access.

What you'll be able to do

  • Trace pointer values, object addresses, sizes, and dereferences through a C memory layout.
  • Explain what malloc and free do to object lifetimes and determine the state of pointers before and after deallocation.
  • Identify leaks, dangling pointers, use-after-free, double frees, and out-of-bounds accesses in short C scenarios.
  • Reason about arrays, strings, structs, and manually managed memory without relying on guesswork about addresses or lifetimes.

Who this is for

This course is for learners who have encountered C before and want to rebuild confidence with pointers and memory. It fits anyone preparing to read, trace, debug, or maintain C code involving arrays, strings, structs, and dynamic allocation.

What you should already know

  • Prior exposure to basic C syntax, including variables, functions, declarations, and statements.
  • Familiarity with compiling and running a small C program.
  • Basic understanding of arrays and structs, even if pointers and dynamic memory feel rusty.

How a lesson actually goes

Lesson 1
TutorWelcome to C Refresher. We will focus on how C objects occupy memory, how pointers access those objects, and how manual allocation changes object lifetimes. By the end, you should be able to trace these states and classify common memory-safety mistakes.
YouI remember that pointers store addresses, but I am not always sure what changes when I use * on one. I also tend to lose track of whether free changes the pointer itself.
TutorThat is a useful distinction to make. We will first separate an object's stored value, its address, and the pointer value; later, we will examine why free ends an object's lifetime but does not automatically erase pointer values that were stored elsewhere.
TutorLet us begin with object representation. Suppose an int object x is stored at address 1000 and occupies four bytes. What information would you use to describe where x is in memory?
YouI would use its address, 1000, and its size, four bytes. I am less clear about alignment—maybe it means the address has to be divisible by four?
TutorYou have the main idea. Alignment is a requirement on which addresses are suitable for an object's type; for many systems an int may need an address aligned to a four-byte boundary, though the exact requirement is implementation-dependent. So we will record address, size, and alignment separately rather than assuming size alone determines every valid address.

Written from this course's first lesson to show the format — not a recording of a real session.

Course content

marks each module's capstone lesson.

01Memory and Pointers4 lessons

Build a mental model of how C objects occupy memory, how addresses identify stored values, and how pointers use those addresses to access data. Learners will trace simple pointer operations and reason about data layout safely.

  • Course Introduction

    Welcome and orientation to a C refresher covering pointers, arrays, strings, structs, and manual memory management. The course develops skills for tracing memory, interpreting pointer behavior, and identifying common memory-safety bugs.

  • Object Representation

    Learn to view variables as regions of memory with locations and storage requirements. Practice interpreting how object size and alignment affect the placement of values in memory.

  • Pointer Dereferencing

    Understand pointers as values that store addresses and use the dereference operator to access the object at a stored address. Distinguish the pointer value from the value of the object it points to when tracing expressions.

  • Pointer and Layout Reasoning

    Synthesize object representation and pointer dereferencing in multi-step memory traces. Identify which accesses are valid, explain the relationship between addresses and stored objects, and detect reasoning errors involving pointer interpretation.

02Dynamic Memory Safety4 lessons

Learn how dynamically allocated objects are created, released, and tracked throughout their lifetimes. Trace heap operations and identify dangling pointers, invalid releases, memory leaks, and other unsafe memory states.

  • malloc Allocation

    Study how malloc requests storage, returns an address, and provides memory whose contents are initially indeterminate. Trace successful and failed allocations using pointer values and object sizes.

  • free Deallocation

    Examine how free releases storage and ends the lifetime of the allocated object. Distinguish the deallocated object from pointer variables that still contain its former address.

  • Dangling Pointers

    Analyze pointers that retain the address of an object after that object's lifetime has ended. Recognize use-after-free and repeated deallocation as consequences of treating such pointers as valid.

  • Memory Safety Synthesis

    Synthesize allocation, deallocation, and pointer-lifetime reasoning to evaluate dynamic-memory traces. Determine object lifetimes, ownership consequences, and the exact point at which memory becomes unsafe or unreachable.

Questions

Is this a first course in C?

No. It is a refresher for learners who already know basic C syntax and want focused practice reasoning about memory, pointers, and allocation.

Will this cover both pointers and dynamic memory?

Yes. The course starts with object representation, pointer dereferencing, and memory layouts, then moves through malloc, free, dangling pointers, and common dynamic-memory errors.

Does it cover arrays, strings, and structs?

They are included as part of the course's core C-memory coverage, with emphasis on how their representation and access relate to pointer and bounds reasoning.

Will I write a large C project?

No. The focus is on short, targeted reasoning exercises and tracing program state rather than building a prescribed application.

Can the tutor help if I confuse an address with a value?

Yes. The one-on-one tutor can ask you to distinguish the pointer value, the object it refers to, and the result of dereferencing it, then adjust explanations and practice based on your answer.

The first lesson is ten minutes away.

Free while codeset is early. You choose what you're building before the first lesson starts, and the course is taught around it.

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