diff --git a/src/matrixMath.c b/src/matrixMath.c
index f9acc51..38d907a 100644
--- a/src/matrixMath.c
+++ b/src/matrixMath.c
@@ -8,31 +8,53 @@
 
 // MATRICES IN COLUMN MAJOR
 
+// Sets a vector to be (0,0,0)T.
 void vec3Zero(vec3* out) {
+	assert(out != NULL);
+
 	for (int i = 0; i < 3; i++) {
 		((GLfloat*)out)[i] = 0;
 	}
 }
 
+// Adds two vectors and writes the result into out.
 void vec3Add(vec3* out, vec3* a, vec3* b) {
+	assert(a != NULL);
+	assert(b != NULL);
+	assert(out != NULL);
+	
 	for (int i = 0; i < 3; i++) {
 		((GLfloat*)out)[i] = ((GLfloat*)a)[i] + ((GLfloat*)b)[i];
 	}
 }
 
+// Multiply a vector by a factor.
 void vec3Multiply(vec3* out, vec3* a, GLfloat x) {
+	assert(out != NULL);
+	assert(a != NULL);
+
 	for (int i = 0; i < 3; i++) {
 		((GLfloat*)out)[i] = ((GLfloat*)a)[i] * x;
 	}
 }
 
+// Divide a vector by another vector.
 void vec3Subtract(vec3* out, vec3* a, vec3* b) {
+	assert(out != NULL);
+	assert(a != NULL);
+	assert(b != NULL);
+
 	vec3 minusB;
 	vec3Multiply(&minusB, b, -1);
 	vec3Add(out, a, &minusB);
 }
 
+// Calculates the cross product of two vectors.
 void vec3Cross(vec3* out, vec3* a, vec3* b) {
+	assert(out != NULL);
+	assert(a != NULL);
+	assert(b != NULL);
+
 	vec3 result;
 	result.x = a->y * b->z - a->z * b->y;
 	result.y = a->z * b->x - a->x * b->z;
@@ -40,19 +62,31 @@ void vec3Cross(vec3* out, vec3* a, vec3* b) {
 	memcpy(out, &result, sizeof(vec3));
 }
 
+// Return the length of a vector.
 GLfloat vec3Length(vec3* a) {
+	assert(a != NULL);
+
 	return (GLfloat)sqrt(a->x * a->x + a->y * a->y + a->z * a->z);
 }
 
+// Return the dot product of a vector.
 GLfloat vec3Dot(vec3* a, vec3* b) {
+	assert(a != NULL);
+	assert(b != NULL);
+
 	return a->x * b->x + a->y * b->y + a->z * b->z;
 }
 
+// Normalise a vector.
 void vec3Normalise(vec3* out, vec3* a) {
+	assert(out != NULL);
+	assert(a != NULL);
 	vec3Multiply(out, a, 1 / vec3Length(a));
 }
 // CREATE 4x4 IDENTITY MATRIX
 void identity(mat4* out) {
+	assert(out != NULL);
+
 	for (int i = 0; i < 16; i++) {
 		((GLfloat*)out)[i] = (i % 4 == i / 4);
 	}
@@ -60,6 +94,8 @@ void identity(mat4* out) {
 
 // CREATE 4x4 TRANSLATION MATRIX
 void translation(mat4* out, vec3* v) {
+	assert(out != NULL);
+
 	identity(out);
 	out->m03 = v->x;
 	out->m13 = v->y;
@@ -68,6 +104,8 @@ void translation(mat4* out, vec3* v) {
 
 // CREATE 4x4 SCALING MATRIX
 void scaling(mat4* out, vec3* v) {
+	assert(out != NULL);
+
 	identity(out);
 	out->m00 = v->x;
 	out->m11 = v->y;
@@ -81,6 +119,7 @@ void scaling(mat4* out, vec3* v) {
  *    0       0     0      1
 */
 void rotationZ(mat4* out, GLfloat angle) {
+	assert(out != NULL);
 	identity(out);
 	out->m00 = cos(angle);
 	out->m10 = sin(angle);
@@ -95,6 +134,8 @@ void rotationZ(mat4* out, GLfloat angle) {
  *    0       0     0      1
 */
 void rotationY(mat4* out, GLfloat angle) {
+	assert(out != NULL);
+
 	identity(out);
 	out->m00 = cos(angle);
 	out->m20 = -sin(angle);
@@ -104,6 +145,8 @@ void rotationY(mat4* out, GLfloat angle) {
 
 // CREATE 4x4 ROTATION MATRIX AROUND Y AXIS
 void rotationX(mat4* out, GLfloat angle) {
+	assert(out != NULL);
+
 	identity(out);
 	out->m11 = cos(angle);
 	out->m21 = sin(angle);
@@ -113,6 +156,10 @@ void rotationX(mat4* out, GLfloat angle) {
 
 // MULTIPLY ANY TWO MATRICES
 void multiplyAny(GLfloat* out, GLfloat* A, GLfloat* B, int wA, int hA, int wB) {
+	assert(out != NULL);
+	assert(A != NULL);
+	assert(B != NULL);
+	
 	int sizeOut = hA * wB;
 	GLfloat* result = (GLfloat*) malloc(sizeOut * sizeof(GLfloat));
 	for (int i = 0; i < sizeOut; i++) {
@@ -128,11 +175,19 @@ void multiplyAny(GLfloat* out, GLfloat* A, GLfloat* B, int wA, int hA, int wB) {
 
 // MULTIPLY TWO 4x4 MATRICES
 void multiply(mat4* out, mat4* A, mat4* B) {
+	assert(out != NULL);
+	assert(A != NULL);
+	assert(B != NULL);
+
 	multiplyAny((GLfloat*)out, (GLfloat*)A, (GLfloat*)B, 4, 4, 4);
 }
 
 // MULTIPLY in WITH TRANSLATION MATRIX OF v
 void translate(mat4* out, mat4* in, vec3* v) {
+	assert(out != NULL);
+	assert(in != NULL);
+	assert(v != NULL);
+
 	mat4 translationMatrix;
 	translation(&translationMatrix, v);
 	multiply(out, &translationMatrix, in);
@@ -140,6 +195,10 @@ void translate(mat4* out, mat4* in, vec3* v) {
 
 // MULTIPLY in WITH SCALING MATRIX OF v
 void scale(mat4* out, mat4* in, vec3* v) {
+	assert(out != NULL);
+	assert(in != NULL);
+	assert(v != NULL);
+
 	mat4 scalingMatrix;
 	scaling(&scalingMatrix, v);
 	multiply(out, &scalingMatrix, in);
@@ -147,18 +206,27 @@ void scale(mat4* out, mat4* in, vec3* v) {
 
 // MULTIPLY in WITH ROTATION MATRIX OF angle AROUND Z AXIS
 void rotateZ(mat4* out, mat4* in, GLfloat angle) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	mat4 rotationMatrix;
 	rotationZ(&rotationMatrix, angle);
 	multiply(out, &rotationMatrix, in);
 }
 // MULTIPLY in WITH ROTATION MATRIX OF angle AROUND Y AXIS
 void rotateY(mat4* out, mat4* in, GLfloat angle) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	mat4 rotationMatrix;
 	rotationY(&rotationMatrix, angle);
 	multiply(out, &rotationMatrix, in);
 }
 // MULTIPLY in WITH ROTATION MATRIX OF angle AROUND X AXIS
 void rotateX(mat4* out, mat4* in, GLfloat angle) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	mat4 rotationMatrix;
 	rotationX(&rotationMatrix, angle);
 	multiply(out, &rotationMatrix, in);
@@ -166,6 +234,9 @@ void rotateX(mat4* out, mat4* in, GLfloat angle) {
 
 // TRANSPOSE MATRIX OF ANY SIZE
 void transposeAny(GLfloat* out, GLfloat* in, int w, int h) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	int size = w * h;
 	GLfloat* result = (GLfloat*) malloc(size * sizeof(GLfloat));
 
@@ -181,11 +252,15 @@ void transposeAny(GLfloat* out, GLfloat* in, int w, int h) {
 
 // TRANSPOSE 4x4 MATRIX
 void transpose(mat4* out, mat4* in) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	transposeAny((GLfloat*)out, (GLfloat*)in, 4, 4);
 }
 
 // PRINT MATRIX OF ANY SIZE
 void printAny(GLfloat* M, int w, int h) {
+	assert(M != NULL);
 	GLfloat* transposed = (GLfloat*) malloc(w * h * sizeof(GLfloat));
 	transposeAny(transposed, M, w, h);
 
@@ -200,19 +275,28 @@ void printAny(GLfloat* M, int w, int h) {
 }
 
 void vec3Print(vec3* a) {
+	assert(a != NULL);
+
 	printAny((GLfloat*)a, 1, 3);
 }
 
 void mat4Print(mat4* m) {
+	assert(m != NULL);
+
 	printAny((GLfloat*)m, 4, 4);
 }
 
 void mat3Print(mat3* m) {
+	assert(m != NULL);
+
 	printAny((GLfloat*)m, 3, 3);
 }
 
 // TURN mat4 INTO mat3 BY CUTTING LAST COLUMN AND ROW
 void mat3From4(mat3* out, mat4* in) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	memcpy(&out->m00, &in->m00, sizeof(vec3));
 	memcpy(&out->m01, &in->m01, sizeof(vec3));
 	memcpy(&out->m02, &in->m02, sizeof(vec3));
@@ -220,6 +304,9 @@ void mat3From4(mat3* out, mat4* in) {
 
 // TRANSPOSE 3x3 MATRIX
 void mat3Transpose(mat3* out, mat3* in) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	transposeAny((GLfloat*)out, (GLfloat*)in, 3, 3);
 }
 
@@ -230,6 +317,9 @@ void mat3Transpose(mat3* out, mat3* in) {
  */
 // GET THE MINOR MATRIX OF A 3x3 MATRIX
 void mat3Minor(mat3* out, mat3* in) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	mat3 result;
 
 	result.m00 = in->m11 * in->m22 - in->m21 * in->m12;
@@ -249,6 +339,9 @@ void mat3Minor(mat3* out, mat3* in) {
 
 // GET THE COFACTOR MATRIX OF A 3x3 MATRIX
 void mat3Cofactor(mat3* out, mat3* in) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	mat3 result;
 	mat3Minor(out, in);
 
@@ -260,12 +353,18 @@ void mat3Cofactor(mat3* out, mat3* in) {
 
 // GET ADJOING MATRRIX OF 3x3 MATRIX
 void mat3Adjoint(mat3* out, mat3* in) {
+	assert(out != NULL);
+	assert(in != NULL);
+	
 	mat3Cofactor(out, in);
 	mat3Transpose(out, out);
 }
 
 // MULTIPLY A 3x3 MATRIX WITH A SCALAR x (componentwise)
 void mat3MultiplyScalar(mat3* out, mat3* in, GLfloat x) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	for (int i = 0; i < 9; i++) {
 		((GLfloat*)out)[i] = ((GLfloat*)in)[i] * x;
 	}
@@ -273,6 +372,8 @@ void mat3MultiplyScalar(mat3* out, mat3* in, GLfloat x) {
 
 // CALCULATE DETERMINANT OF 3x3 MATRIX
 GLfloat mat3Determinant(mat3* M) {
+	assert(M != NULL);
+
 	return
 		  M->m00 * M->m11 * M->m22
 		+ M->m01 * M->m12 * M->m20
@@ -286,6 +387,9 @@ GLfloat mat3Determinant(mat3* M) {
 
 // GET INVERSE OF 3x3 MATRIX
 void mat3Inverse(mat3* out, mat3* in) {
+	assert(out != NULL);
+	assert(in != NULL);
+
 	mat3 result;
 	mat3Adjoint(&result, in);
 	mat3MultiplyScalar(&result, &result, 1 / mat3Determinant(in));
@@ -293,8 +397,11 @@ void mat3Inverse(mat3* out, mat3* in) {
 	memcpy(out, &result, sizeof(mat3));
 }
 
-// GET THE SUM OF DIFFERENCES BETWEEON TWO MATRICES
+// GET THE SUM OF DIFFERENCES BETWEEN TWO MATRICES
 GLfloat sumDiffAny(GLfloat* A, GLfloat* B, int w, int h) {
+	assert(A != NULL);
+	assert(B != NULL);
+
 	GLfloat result = 0;
 	for (int i = 0; i < w * h; i++) {
 		result += fabs(A[i] - B[i]);
@@ -304,11 +411,18 @@ GLfloat sumDiffAny(GLfloat* A, GLfloat* B, int w, int h) {
 
 // GET THE SUM OF DIFFERENCES BETWEEN TWO 3x3 MATRICES
 GLfloat mat3SumDiff(mat3* A, mat3* B) {
+	assert(A != NULL);
+	assert(B != NULL);
+
 	return sumDiffAny((GLfloat*)A, (GLfloat*)B, 3, 3);
 }
 
 // COMPONENTWISE SUBTRACT vec2 b FROM vec2 a
 void vec2Subtract(vec2* out, vec2* a, vec2* b) {
+	assert(out != NULL);
+	assert(a != NULL);
+	assert(b != NULL);
+
 	out->x = a->x - b->x;
 	out->y = a->y - b->y;
 }
\ No newline at end of file