Your mission
Your first compiled C program. One job: output a specific line and exit cleanly.
See it in action
./helloHello World!
Your checklist
Constraints
- Expected file
hello.c- Allowed functions
write
100% free
“Wrong answer” teaches nothing.
Write C in the browser, graded byte for byte. Every failing test names the line, the column, the byte. The full verdict, Valgrind included, lands in milliseconds.
2 of 2 failing
Built for how you actually learn
Learn C
Seven chapters, from your first program down to the system underneath. Each chapter ends on a timed checkpoint.
CHAPTER CHECKPOINT
C foundations checkpoint
60 min100% to validate
Unlocks at 280 Chapter XP or when every required exercise is passed.
Required exercises20 / 29
Chapter XP216 / 280
Visualizer
Step through your program and watch the stack, the heap and every pointer between them.
Stack
main()
L26
checksint *Block 1
demot_attempt
.studentconst char *"Grady"
.scoreint40
final_scoreint?
grade(attempt, bonus)
L12
attemptt_attempt *demo
bonusint2
Heap
Block 1
8 B
1011
Literal
const char
"Grady"\0Stack
main()
L26
checksint *Block 1
Heap
Block 1
8 B
1011
GitHub sync
Publish your passing solutions to a repository you own.
Challenges
A series of exercises against one clock, level after level, the way an exam runs.
Foundations 1
Level 3 of 8Score 25 of 100
0s
12345678
CLI
Take challenges in your terminal, with your own editor.
Studio
Write your own exercises and challenges, with their tests. Share them with everyone.
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