diff --git a/src/util/binary.sh b/src/util/binary.sh
new file mode 100644
index 0000000..629a72d
--- /dev/null
+++ b/src/util/binary.sh
@@ -0,0 +1,36 @@
+#!/bin/bash
+#
+# https://github.com/EngineeringSoftware/gobash/blob/main/LICENSE
+#
+# Util functions to manipulate binary numbers.
+
+if [ -n "${BINARY_MOD:-}" ]; then return 0; fi
+readonly BINARY_MOD=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
+
+. ${BINARY_MOD}/../lang/p.sh
+
+
+# ----------
+# Functions.
+
+function binary_d2b() {
+        # From decimal to binary.
+        local ctx; is_ctx "${1}" && ctx="${1}" && shift
+        [ $# -ne 1 ] && { ctx_wn $ctx; return $EC; }
+        local -r n="${1}"
+        shift 1 || { ctx_wn $ctx; return $EC; }
+
+        # TODO: check for errors.
+        echo "obase=2; ${n}" | bc
+}
+
+function binary_b2d() {
+        # From binary to decimal.
+        local ctx; is_ctx "${1}" && ctx="${1}" && shift
+        [ $# -ne 1 ] && { ctx_wn $ctx; return $EC; }
+        local -r n="${1}"
+        shift 1 || { ctx_wn $ctx; return $EC; }
+
+        # TODO: check for errors.
+        echo "ibase=2;obase=A; ${n}" | bc
+}
diff --git a/src/util/binary_test.sh b/src/util/binary_test.sh
new file mode 100644
index 0000000..c2d6e96
--- /dev/null
+++ b/src/util/binary_test.sh
@@ -0,0 +1,48 @@
+#!/bin/bash
+#
+# https://github.com/EngineeringSoftware/gobash/blob/main/LICENSE
+#
+# Unit tests for the binary functions.
+
+if [ -n "${BINARY_TEST_MOD:-}" ]; then return 0; fi
+readonly BINARY_TEST_MOD=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
+
+. ${BINARY_TEST_MOD}/binary.sh
+. ${BINARY_TEST_MOD}/../testing/bunit.sh
+
+
+# ----------
+# Functions.
+
+function test_binary_d2b() {
+        local res
+
+        res=$(binary_d2b "3")
+        [ "${res}" = "11" ] || \
+                assert_fail
+
+        res=$(binary_d2b "33")
+        [ "${res}" = "100001" ] || \
+                assert_fail
+
+        return 0
+}
+readonly -f test_binary_d2b
+
+function test_binary_b2d() {
+        local res
+
+        res=$(binary_b2d "011")
+        [ "${res}" = "3" ] || \
+                assert_fail
+
+        res=$(binary_b2d "100001")
+        [ "${res}" = "33" ] || \
+                assert_fail
+
+        #binary_b2d "100001a" && \
+                #assert_fail
+
+        return 0
+}
+readonly -f test_binary_b2d
diff --git a/src/util/char.sh b/src/util/char.sh
new file mode 100644
index 0000000..fc6520d
--- /dev/null
+++ b/src/util/char.sh
@@ -0,0 +1,23 @@
+#!/bin/bash
+#
+# https://github.com/EngineeringSoftware/gobash/blob/main/LICENSE
+#
+# Util char functions.
+
+if [ -n "${CHAR_MOD:-}" ]; then return 0; fi
+readonly CHAR_MOD=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
+
+. ${CHAR_MOD}/../lang/p.sh
+
+
+# ----------
+# Functions.
+
+function char_alphabet() {
+        # Print alphabet on a single line.
+        local ctx; is_ctx "${1}" && ctx="${1}" && shift
+        [ $# -ne 0 ] && { ctx_wn $ctx; return $EC; }
+        shift 0 || { ctx_wn $ctx; return $EC; }
+
+        echo {a..z}
+}
diff --git a/src/util/p.sh b/src/util/p.sh
index 8423d5a..a444608 100644
--- a/src/util/p.sh
+++ b/src/util/p.sh
@@ -14,7 +14,9 @@ readonly UTIL_PACKAGE=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
 . ${UTIL_PACKAGE}/math.sh
 . ${UTIL_PACKAGE}/rand.sh
 . ${UTIL_PACKAGE}/strings.sh
+. ${UTIL_PACKAGE}/char.sh
 . ${UTIL_PACKAGE}/regexp.sh
 . ${UTIL_PACKAGE}/flags.sh
 . ${UTIL_PACKAGE}/complex.sh
 . ${UTIL_PACKAGE}/user.sh
+. ${UTIL_PACKAGE}/binary.sh