diff --git a/meson.build b/meson.build
index 4339f9c..c3939ff 100644
--- a/meson.build
+++ b/meson.build
@@ -45,4 +45,21 @@ c_5_lab_5_1 = executable(
   install: true,
 )
 
-c_6_lab_6 = executable('c_6_lab-6', ['src/chapter_6/lab-6/main.cpp', 'src/chapter_6/lab-6/IntVector.h', 'src/chapter_6/lab-6/IntVector.cpp'], install: true)
+c_6_lab_6 = executable(
+  'c_6_lab-6',
+  [
+    'src/chapter_6/lab-6/main.cpp',
+    'src/chapter_6/lab-6/IntVector.h',
+    'src/chapter_6/lab-6/IntVector.cpp',
+  ],
+  install: true,
+)
+c_6_program_4 = executable(
+  'c_6_program-4',
+  [
+    'src/chapter_6/program-4/main.cpp',
+    'src/chapter_6/program-4/IntVector.h',
+    'src/chapter_6/program-4/IntVector.cpp',
+  ],
+  install: true,
+)
diff --git a/src/chapter_6/program-4/IntVector.cpp b/src/chapter_6/program-4/IntVector.cpp
new file mode 100644
index 0000000..bd92023
--- /dev/null
+++ b/src/chapter_6/program-4/IntVector.cpp
@@ -0,0 +1,149 @@
+#include "IntVector.h"
+#include <stdexcept>
+using namespace std;
+
+IntVector::IntVector(unsigned capacity, int value) {
+  __size = capacity;
+  __capacity = capacity;
+
+  if (__size > 0) {
+    __data = new int[__size];
+  } else {
+    __data = nullptr;
+  }
+
+  for (unsigned i = 0; i < __size; i++) {
+    __data[i] = value;
+  }
+}
+
+IntVector::~IntVector() { delete[] __data; }
+
+const int &IntVector::at(unsigned index) const {
+  if (index >= __size)
+    throw out_of_range("IntVector::at_range_check");
+
+  return __data[index];
+}
+
+int &IntVector::at(unsigned index) {
+  if (index >= __size)
+    throw out_of_range("IntVector::at_range_check");
+
+  return __data[index];
+}
+
+unsigned IntVector::size() const { return __size; }
+unsigned IntVector::capacity() const { return __capacity; };
+bool IntVector::empty() const { return __size == 0; };
+const int &IntVector::front() const { return __data[0]; }
+const int &IntVector::back() const { return __data[__size - 1]; }
+
+int &IntVector::front() { return __data[0]; };
+int &IntVector::back() { return __data[__size - 1]; };
+void IntVector::reserve(unsigned n) {
+  if (n <= __capacity) {
+    return;
+  }
+  expand(n - __capacity);
+};
+
+void IntVector::clear() { __size = 0; };
+
+void IntVector::expand(unsigned amount) {
+  __capacity += amount;
+  int *newVec = new int[__capacity];
+  for (unsigned i = 0; i < __size; i++) {
+    newVec[i] = __data[i];
+  }
+  delete[] __data;
+  __data = newVec;
+}
+
+void IntVector::expand() {
+  if (__capacity == 0) {
+    expand(1);
+    return;
+  }
+  expand(__capacity);
+}
+
+void IntVector::push_back(int value) {
+  if (__size >= __capacity) {
+    expand();
+  }
+  __size++;
+  back() = value;
+};
+
+void IntVector::assign(unsigned n, int value) {
+  if (n > __capacity && n - __capacity > __capacity) {
+    expand(n - __capacity);
+  } else if (n > __capacity) {
+    expand();
+  }
+
+  delete[] __data;
+  __data = new int[__capacity];
+
+  __size = n;
+
+  for (unsigned i = 0; i < __size; i++) {
+    __data[i] = value;
+  }
+};
+
+void IntVector::pop_back() { __size--; };
+
+void IntVector::resize(unsigned n, int value) {
+  if (n == __size)
+    return;
+
+  if (n < __size) {
+    __size = n;
+    return;
+  }
+
+  if (n > __capacity) {
+    if (n - __capacity > __capacity) {
+      reserve(n);
+    } else {
+      expand();
+    }
+
+    int *newVec = new int[__capacity];
+    for (unsigned i = 0; i < __size; i++) {
+      newVec[i] = __data[i];
+    }
+    delete[] __data;
+    __data = newVec;
+  }
+
+  for (; __size < n; __size++) {
+    __data[__size] = value;
+  }
+};
+
+void IntVector::insert(unsigned idx, int value) {
+  if (idx > __size) {
+    throw out_of_range("IntVector::insert_range_check");
+  }
+  if (__size == __capacity) {
+    expand();
+  }
+  __size++;
+  for (unsigned i = idx; i < __size - 1; i++) {
+    __data[i + 1] = __data[i];
+  }
+  __data[idx] = value;
+}
+
+void IntVector::erase(unsigned idx) {
+  if (idx >= __size) {
+    throw out_of_range("IntVector::erase_range_check");
+  }
+  for (unsigned i = idx; i < __size - 1; i++) {
+    __data[i] = __data[i + 1];
+  }
+  __size--;
+}
diff --git a/src/chapter_6/program-4/IntVector.h b/src/chapter_6/program-4/IntVector.h
new file mode 100644
index 0000000..13aabc0
--- /dev/null
+++ b/src/chapter_6/program-4/IntVector.h
@@ -0,0 +1,31 @@
+#pragma once
+
+class IntVector {
+public:
+  IntVector(unsigned capacity = 0, int value = 0);
+  ~IntVector();
+  unsigned size() const;
+  unsigned capacity() const;
+  bool empty() const;
+  const int &at(unsigned index) const;
+  const int &front() const;
+  const int &back() const;
+  int &at(unsigned index);
+  int &front();
+  int &back();
+  void assign(unsigned, int);
+  void push_back(int value);
+  void pop_back();
+  void clear();
+  void resize(unsigned n, int value = 0);
+  void reserve(unsigned n);
+  void insert(unsigned, int);
+  void erase(unsigned);
+
+private:
+  unsigned __size;
+  unsigned __capacity;
+  int *__data;
+  void expand();
+  void expand(unsigned);
+};
diff --git a/src/chapter_6/program-4/main.cpp b/src/chapter_6/program-4/main.cpp
new file mode 100644
index 0000000..9e20d9b
--- /dev/null
+++ b/src/chapter_6/program-4/main.cpp
@@ -0,0 +1,180 @@
+#include "IntVector.h"
+#include <cassert>
+#include <iostream>
+#include <stdexcept>
+using namespace std;
+
+int main() {
+  cout << "Running test bench!" << endl;
+
+  IntVector *testVec = nullptr;
+
+  testVec = new IntVector();
+  assert(testVec->empty());
+  cout << "[SUCCESS] empty() works as expected for empty vector." << endl;
+  assert(testVec->size() == 0);
+  assert(testVec->capacity() == 0);
+  cout << "[SUCCESS] Default constructor sets size and capacity properly."
+       << endl;
+
+  delete testVec;
+  testVec = new IntVector(1);
+  assert(!testVec->empty());
+  cout << "[SUCCESS] empty() works as expected for nonempty vector." << endl;
+  assert(testVec->at(0) == 0);
+  cout << "[SUCCESS] Basic vector initialization works." << endl;
+
+  for (unsigned i = 0; i < 100; i++) {
+    delete testVec;
+    testVec = new IntVector(i, 50 - i);
+
+    assert(testVec->capacity() == i);
+    assert(testVec->size() == i);
+
+    for (unsigned j = 0; j < testVec->size(); j++) {
+      assert(testVec->at(j) == 50 - static_cast<int>(i));
+    }
+  }
+
+  cout << "[SUCCESS] Size and capacity work as expected" << endl;
+  cout << "[SUCCESS] Initializing values getting values at indices work."
+       << endl;
+
+  delete testVec;
+  testVec = new IntVector(5, 2);
+
+  bool failed = false;
+  try {
+    testVec->at(5);
+  } catch (const out_of_range &e) {
+    failed = true;
+  }
+  assert(failed);
+  cout << "[SUCCESS] at() correctly throws for out of range access." << endl;
+
+  assert((testVec->front() == testVec->at(0)));
+  cout << "[SUCCESS] Output of front() is consistent with output of at(0)."
+       << endl;
+
+  assert(testVec->front() == 2);
+  cout << "[SUCCESS] Output of front() is correct." << endl;
+
+  assert((testVec->back() == testVec->at(testVec->size() - 1)));
+  cout
+      << "[SUCCESS] Output of back() is consistent with output of at(size - 1)."
+      << endl;
+
+  assert(testVec->front() == 2);
+  cout << "[SUCCESS] Output of back() is correct." << endl;
+
+  delete testVec;
+  testVec = new IntVector(5);
+  assert(testVec->capacity() == 5);
+  testVec->reserve(20);
+  assert(testVec->capacity() == 20);
+  testVec->reserve(5);
+  assert(testVec->capacity() == 20);
+  cout << "[SUCCESS] reserve() works as expected." << endl;
+
+  testVec->clear();
+  assert(testVec->capacity() == 20);
+  assert(testVec->size() == 0);
+  assert(testVec->empty());
+  cout << "[SUCCESS] clear() works as expected." << endl;
+
+  delete testVec;
+  testVec = new IntVector(5);
+  testVec->at(3) = 2;
+  assert(testVec->back() == 0);
+  testVec->pop_back();
+  assert(testVec->size() == 4);
+  assert(testVec->back() == 2);
+  cout << "[SUCCESS] pop_back() works as expected." << endl;
+
+  delete testVec;
+  testVec = new IntVector(5);
+  testVec->push_back(5);
+  assert(testVec->size() == 6);
+  assert(testVec->back() == 5);
+  cout << "[SUCCESS] push_back() works as expected." << endl;
+
+  delete testVec;
+  testVec = new IntVector(5);
+  testVec->resize(3, 2);
+  assert(testVec->size() == 3);
+  assert(testVec->capacity() == 5);
+  assert(testVec->front() == 0);
+  cout << "[SUCCESS] resize() to lesser capacity works." << endl;
+  testVec->resize(8);
+  assert(testVec->size() == 8);
+  assert(testVec->capacity() == 10);
+  assert(testVec->back() == 0);
+  cout << "[SUCCESS] resize() doubles capacity when appropriate." << endl;
+  testVec->resize(100, 5);
+  assert(testVec->size() == 100);
+  assert(testVec->capacity() == 100);
+  assert(testVec->back() == 5);
+  testVec->resize(500);
+  assert(testVec->capacity() == 500);
+  assert(testVec->size() == 500);
+  assert(testVec->back() == 0);
+  cout << "[SUCCESS] resize() increases capacity when appropriate." << endl;
+
+  delete testVec;
+  testVec = new IntVector(5);
+  testVec->assign(3, 10);
+  assert(testVec->size() == 3);
+  assert(testVec->capacity() == 5);
+  assert(testVec->at(1) == 10);
+  testVec->assign(8, 0);
+  assert(testVec->capacity() == 10);
+  assert(testVec->front() == 0);
+  testVec->assign(50, 2);
+  assert(testVec->capacity() == 50);
+  assert(testVec->front() == 2);
+  cout << "[SUCCESS] assign() works as expected." << endl;
+
+  delete testVec;
+  testVec = new IntVector(5);
+  testVec->insert(3, 3);
+  assert(testVec->at(3) == 3);
+  assert(testVec->size() == 6);
+  testVec->insert(3, 3);
+  assert(testVec->size() == 7);
+  assert(testVec->capacity() == 10);
+  failed = false;
+  cout << "[SUCCESS] Basic insertion works" << endl;
+  try {
+    testVec->insert(10, 3);
+  } catch (const out_of_range &e) {
+    failed = true;
+  }
+  assert(failed);
+  cout << "[SUCCESS] insert() correctly throws exception when out of range"
+       << endl;
+
+  delete testVec;
+  testVec = new IntVector(5);
+  testVec->erase(3);
+  assert(testVec->size() == 4);
+  cout << "[SUCCESS] erase() modifies size properly." << endl;
+  testVec->insert(3, 4);
+  testVec->erase(3);
+  assert(testVec->at(3) == 0);
+  cout << "[SUCCESS] erase() removes the correct element." << endl;
+  assert(testVec->capacity() == 5);
+  cout << "[SUCCESS] erase() doesn't modify capacity" << endl;
+  failed = false;
+  try {
+    testVec->erase(10);
+  } catch (const out_of_range &e) {
+    failed = true;
+  }
+  assert(failed);
+  cout << "[SUCCESS] insert() correctly throws exception when out of range"
+       << endl;
+
+  delete testVec;
+  testVec = nullptr;
+  cout << "All tests passed!" << endl;
+}