diff --git a/histogram.cpp b/histogram.cpp
new file mode 100644
index 0000000..663a6d3
--- /dev/null
+++ b/histogram.cpp
@@ -0,0 +1,77 @@
+#include <iostream>
+#include <vector>
+#include <cmath>
+#include "histogram.h"
+
+using namespace std;
+
+void
+find_minmax(const vector<double>& numbers, double& min1, double& max1)
+{
+    max1 = numbers[0];
+    min1 = numbers[0];
+    for(size_t i = 0; i < numbers.size(); i++)
+    {
+        if (numbers[i] > max1) max1 = numbers[i];
+        if (numbers[i] < min1) min1 = numbers[i];
+    }
+    return;
+}
+
+vector<double>
+make_histogram(const vector<double>& numbers, size_t bin_count)
+{
+    double min1, max1;
+    find_minmax(numbers, min1, max1);
+
+    vector<double> bins;
+    bins.resize(bin_count);
+
+    size_t cor_size = (max1 - min1)/bin_count;
+
+    for (size_t i = 0; i < numbers.size(); i++)
+    {
+        bool flag = false;
+        for (size_t j = 0; (j < bin_count) && !flag; j++)
+        {
+            auto L = min1 + j*cor_size;
+            auto H = min1 + (j+1)*cor_size;
+            if ((L <= numbers[i]) && (numbers[i] <= H))
+            {
+                flag = true;
+                bins[j]++;
+            }
+        }
+        if (!flag) bins[bin_count-1]++;
+    }
+
+    return bins;
+}
+
+void
+show_histogram_text(vector<double> bins, const vector<double>& numbers, size_t bin_count)
+{
+    const size_t MAX_ASTERISK = 76;
+    size_t maxb = bins[0];
+    size_t H, j;
+
+    for (j = 1; j < bin_count; j++)
+    {
+        if (bins[j] > maxb) maxb = bins[j];
+    }
+
+    for (j = 0; j < bin_count; j++)
+    {
+        if (maxb > MAX_ASTERISK)
+        {
+            H  = MAX_ASTERISK * (static_cast<double>(bins[j]) / maxb);
+        }
+        else H = bins[j];
+        if (bins[j] < 100) cout << " ";
+        if (bins[j] < 10) cout << " ";
+        cout << bins[j] << "|";
+        for (size_t i = 0; i < H; i++) cout << "*";
+        cout << endl;
+    }
+    return;
+}
diff --git a/histogram.h b/histogram.h
new file mode 100644
index 0000000..e629077
--- /dev/null
+++ b/histogram.h
@@ -0,0 +1,7 @@
+#pragma once
+#include <vector>
+
+std::vector<double>
+make_histogram(const std::vector<double>& numbers, size_t bin_count);
+void
+show_histogram_text(std::vector<double> bins, const std::vector<double>& numbers, size_t bin_count);
diff --git a/histogram_internal.h b/histogram_internal.h
new file mode 100644
index 0000000..627b9f6
--- /dev/null
+++ b/histogram_internal.h
@@ -0,0 +1,5 @@
+#pragma once
+#include <vector>
+
+void
+find_minmax(const std::vector<double>& numbers, double& min1, double& max1);
diff --git a/unittest.cbp b/unittest.cbp
new file mode 100644
index 0000000..6da4486
--- /dev/null
+++ b/unittest.cbp
@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
+<CodeBlocks_project_file>
+	<FileVersion major="1" minor="6" />
+	<Project>
+		<Option title="unittest" />
+		<Option pch_mode="2" />
+		<Option compiler="gcc" />
+		<Build>
+			<Target title="Debug">
+				<Option output="bin/Debug/unittest" prefix_auto="1" extension_auto="1" />
+				<Option object_output="obj/Debug/" />
+				<Option type="1" />
+				<Option compiler="gcc" />
+				<Compiler>
+					<Add option="-g" />
+				</Compiler>
+			</Target>
+			<Target title="Release">
+				<Option output="bin/Release/unittest" prefix_auto="1" extension_auto="1" />
+				<Option object_output="obj/Release/" />
+				<Option type="1" />
+				<Option compiler="gcc" />
+				<Compiler>
+					<Add option="-O2" />
+				</Compiler>
+				<Linker>
+					<Add option="-s" />
+				</Linker>
+			</Target>
+		</Build>
+		<Compiler>
+			<Add option="-Wall" />
+		</Compiler>
+		<Extensions />
+	</Project>
+</CodeBlocks_project_file>
diff --git a/unittest.cpp b/unittest.cpp
new file mode 100644
index 0000000..981aa6f
--- /dev/null
+++ b/unittest.cpp
@@ -0,0 +1,36 @@
+#define DOCTEST_CONFIG_NO_MULTITHREADING
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest.h"
+#include "histogram_internal.h"
+
+TEST_CASE("distinct positive numbers") {
+    double min = 0;
+    double max = 0;
+    find_minmax({1, 2}, min, max);
+    CHECK(min == 1);
+    CHECK(max == 2);
+}
+
+TEST_CASE("distinct identical numbers") {
+    double min = 0;
+    double max = 0;
+    find_minmax({5, 5}, min, max);
+    CHECK(min == 5);
+    CHECK(max == 5);
+}
+
+TEST_CASE("distinct one number") {
+    double min = 0;
+    double max = 0;
+    find_minmax({3}, min, max);
+    CHECK(min == 3);
+    CHECK(max == 3);
+}
+
+TEST_CASE("distinct negative numbers") {
+    double min = 0;
+    double max = 0;
+    find_minmax({-3, -1}, min, max);
+    CHECK(min == -3);
+    CHECK(max == -1);
+}